The Collaborative International Dictionary of English v.0.48:

Block \Block\ (bl[o^]k), v. t. [imp. & p. p. Blocked
   (bl[o^]kt); p. pr. & vb. n. Blocking.] [Cf. F. bloquer, fr.
   bloc block. See Block, n.]
   1. To obstruct so as to prevent passage or progress; to
      prevent passage from, through, or into, by obstructing the
      way; -- used both of persons and things; -- often followed
      by up; as, to block up a road or harbor; to block an
      entrance.
      [1913 Webster]

            With moles . . . would block the port. --Rowe.
      [1913 Webster]

            A city . . . besieged and blocked about. --Milton.
      [1913 Webster]

   2. To secure or support by means of blocks; to secure, as two
      boards at their angles of intersection, by pieces of wood
      glued to each.
      [1913 Webster]

   3. To shape on, or stamp with, a block; as, to block a hat.
      [1913 Webster]

   4. to cause (any activity) to halt by creating an
      obstruction; as, to block a nerve impulse; to block a
      biochemical reaction with a drug.
      [PJC]

   To block out, to begin to reduce to shape; to mark out
      roughly; to lay out; to outline; as, to block out a plan.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Block \Block\ (bl[o^]k), n. [OE. blok; cf. F. bloc (fr. OHG.),
   D. & Dan. blok, Sw. & G. block, OHG. bloch. There is also an
   OHG. bloch, biloh; bi by + the same root as that of E. lock.
   Cf. Block, v. t., Blockade, and see Lock.]
   [1913 Webster]
   1. A piece of wood more or less bulky; a solid mass of wood,
      stone, etc., usually with one or more plane, or
      approximately plane, faces; as, a block on which a butcher
      chops his meat; a block by which to mount a horse;
      children's playing blocks, etc.
      [1913 Webster]

            Now all our neighbors' chimneys smoke,
            And Christmas blocks are burning.     --Wither.
      [1913 Webster]

            All her labor was but as a block
            Left in the quarry.                   --Tennyson.
      [1913 Webster]

   2. The solid piece of wood on which condemned persons lay
      their necks when they are beheaded.
      [1913 Webster]

            Noble heads which have been brought to the block.
                                                  --E. Everett.
      [1913 Webster]

   3. The wooden mold on which hats, bonnets, etc., are shaped.
      Hence: The pattern or shape of a hat.
      [1913 Webster]

            He wears his faith but as the fashion of his hat; it
            ever changes with the next block.     --Shak.
      [1913 Webster]

   4. A large or long building divided into separate houses or
      shops, or a number of houses or shops built in contact
      with each other so as to form one building; a row of
      houses or shops.
      [1913 Webster]

   5. A square, or portion of a city inclosed by streets,
      whether occupied by buildings or not.
      [1913 Webster]

            The new city was laid out in rectangular blocks,
            each block containing thirty building lots. Such an
            average block, comprising 282 houses and covering
            nine acres of ground, exists in Oxford Street.
                                                  --Lond. Quart.
                                                  Rev.
      [1913 Webster]

   6. A grooved pulley or sheave incased in a frame or shell
      which is provided with a hook, eye, or strap, by which it
      may be attached to an object. It is used to change the
      direction of motion, as in raising a heavy object that can
      not be conveniently reached, and also, when two or more
      such sheaves are compounded, to change the rate of motion,
      or to exert increased force; -- used especially in the
      rigging of ships, and in tackles.
      [1913 Webster]

   7. (Falconry) The perch on which a bird of prey is kept.
      [1913 Webster]

   8. Any obstruction, or cause of obstruction; a stop; a
      hindrance; an obstacle; -- also called blockage; as, a
      block in the way; a block in an artery; a block in a
      nerve; a block in a biochemical pathway.
      [1913 Webster]

   9. A piece of box or other wood for engravers' work.
      [1913 Webster]

   10. (Print.) A piece of hard wood (as mahogany or cherry) on
       which a stereotype or electrotype plate is mounted to
       make it type high.
       [1913 Webster]

   11. A blockhead; a stupid fellow; a dolt. [Obs.]
       [1913 Webster]

             What a block art thou !              --Shak.
       [1913 Webster]

   12. A section of a railroad where the block system is used.
       See Block system, below.
       [1913 Webster]

   13. In Australia, one of the large lots into which public
       land, when opened to settlers, is divided by the
       government surveyors.
       [Webster 1913 Suppl.]

   14. (Cricket)
       (a) The position of a player or bat when guarding the
           wicket.
       (b) A block hole.
       (c) The popping crease. [R.]
           [Webster 1913 Suppl.]

   15. a number of individual items sold as a unit; as, a block
       of airline ticketes; a block of hotel rooms; a block of
       stock.
       [PJC]

   16. the length of one side of a city block[5], traversed
       along any side; as, to walk three blocks ahead and turn
       left at the corner.
       [PJC]

   17. a halt in a mental process, especially one due to stress,
       memory lapse, confusion, etc.; as, a writer's block; to
       have a block in remembering a name.
       [PJC]

   18. (computers) a quantity of binary-encoded information
       transferred, or stored, as a unit to, from, or on a data
       storage device; as, to divide a disk into 512-byte
       blocks.
       [PJC]

   19. (computers) a number of locations in a random-access
       memory allocated to storage of specific data; as, to
       allocate a block of 1024 bytes for the stack.
       [PJC]

   A block of shares (Stock Exchange), a large number of
      shares in a stock company, sold in a lump. --Bartlett.

   Block printing.
       (a) A mode of printing (common in China and Japan) from
           engraved boards by means of a sheet of paper laid on
           the linked surface and rubbed with a brush. --S. W.
           Williams.
       (b) A method of printing cotton cloth and paper hangings
           with colors, by pressing them upon an engraved
           surface coated with coloring matter.

   Block system on railways, a system by which the track is
      divided into sections of three or four miles, and trains
      are so run by the guidance of electric signals that no
      train enters a section or block before the preceding train
      has left it.

   Back blocks, Australian pastoral country which is remote
      from the seacoast or from a river.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

block
    n 1: a solid piece of something (usually having flat rectangular
         sides); "the pyramids were built with large stone blocks"
    2: a rectangular area in a city surrounded by streets and
       usually containing several buildings; "he lives in the next
       block" [syn: block, city block]
    3: a three-dimensional shape with six square or rectangular
       sides [syn: block, cube]
    4: a number or quantity of related things dealt with as a unit;
       "he reserved a large block of seats"; "he held a large block
       of the company's stock"
    5: housing in a large building that is divided into separate
       units; "there is a block of classrooms in the west wing"
    6: (computer science) a sector or group of sectors that function
       as the smallest data unit permitted; "since blocks are often
       defined as a single sector, the terms `block' and `sector'
       are sometimes used interchangeably"
    7: an inability to remember or think of something you normally
       can do; often caused by emotional tension; "I knew his name
       perfectly well but I had a temporary block" [syn: block,
       mental block]
    8: a simple machine consisting of a wheel with a groove in which
       a rope can run to change the direction or point of
       application of a force applied to the rope [syn: pulley,
       pulley-block, pulley block, block]
    9: a metal casting containing the cylinders and cooling ducts of
       an engine; "the engine had to be replaced because the block
       was cracked" [syn: engine block, cylinder block, block]
    10: an obstruction in a pipe or tube; "we had to call a plumber
        to clear out the blockage in the drainpipe" [syn:
        blockage, block, closure, occlusion, stop,
        stoppage]
    11: a platform from which an auctioneer sells; "they put their
        paintings on the block" [syn: auction block, block]
    12: the act of obstructing or deflecting someone's movements
        [syn: blocking, block]
    v 1: render unsuitable for passage; "block the way"; "barricade
         the streets"; "stop the busy road" [syn: barricade,
         block, blockade, stop, block off, block up,
         bar]
    2: hinder or prevent the progress or accomplishment of; "His
       brother blocked him at every turn" [syn: obstruct,
       blockade, block, hinder, stymie, stymy,
       embarrass]
    3: stop from happening or developing; "Block his election";
       "Halt the process" [syn: stop, halt, block, kibosh]
    4: interfere with or prevent the reception of signals; "Jam the
       Voice of America"; "block the signals emitted by this
       station" [syn: jam, block]
    5: run on a block system; "block trains"
    6: interrupt the normal function of by means of anesthesia;
       "block a nerve"; "block a muscle"
    7: shut out from view or get in the way so as to hide from
       sight; "The thick curtain blocked the action on the stage";
       "The trees obstruct my view of the mountains" [syn:
       obstruct, block]
    8: stamp or emboss a title or design on a book with a block;
       "block the book cover"
    9: obstruct; "My nose is all stuffed"; "Her arteries are
       blocked" [syn: stuff, lug, choke up, block] [ant:
       loosen up, unstuff]
    10: block passage through; "obstruct the path" [syn: obstruct,
        obturate, impede, occlude, jam, block, close up]
        [ant: disengage, free]
    11: support, secure, or raise with a block; "block a plate for
        printing"; "block the wheels of a car"
    12: impede the movement of (an opponent or a ball); "block an
        attack" [syn: parry, block, deflect]
    13: be unable to remember; "I'm drawing a blank"; "You are
        blocking the name of your first wife!" [syn: forget,
        block, blank out, draw a blank] [ant: call back,
        call up, recall, recollect, remember, retrieve,
        think]
    14: shape by using a block; "Block a hat"; "block a garment"
    15: shape into a block or blocks; "block the graphs so one can
        see the results clearly"
    16: prohibit the conversion or use of (assets); "Blocked funds";
        "Freeze the assets of this hostile government" [syn:
        freeze, block, immobilize, immobilise] [ant: free,
        release, unblock, unfreeze]

Moby Thesaurus II by Grady Ward, 1.0:

464 Moby Thesaurus words for "block":
   Boeotian, Dutch auction, afterthought, agate, agnosia, apply to,
   aquatint, arm, arrest, auction, auction block, auction sale,
   autolithograph, ax, balk, ball, bar, barricade, barrier,
   baseball bat, bat, batch, battery, battledore, bauble, beat off,
   bind, blank wall, blanket, blind alley, blind gut, block out,
   block print, block up, blockade, blockage, blocking, blocks,
   blot out, board lot, body, bolt, bottleneck, brake, brick,
   bring to, bring up short, bulk, bung, bung up, bureaucratic delay,
   cake, canopy, catch, caulk, cecum, censorship, check, checkerboard,
   checkmate, chessboard, chink, chock, choke, choke off, choke up,
   choking, choking off, chromolithograph, chunk, city block, cloak,
   clod, clog, clog up, clos, close, close off, close tight, close up,
   clothe, cloud, club, clump, cluster, cockhorse, color print,
   concrete, concretion, confine, congest, congestion, conglomerate,
   conglomeration, constipate, constipation, constrict, conversion,
   cope, copperplate, copperplate print, cordon, cork, costiveness,
   counter, cover, cover up, cowl, crayon engraving, cricket bat,
   croft, cross, crowd, cube, cue, cul-de-sac, curtain, cut, cut off,
   cut short, dam, dam up, dead end, deadlock, death chair,
   death chamber, debar, defense mechanism, delay, delayage,
   delayed reaction, delirium, delusion, delusion of persecution,
   deny, design, detain, detention, determent, deterrent, difficulty,
   dimwit, disorientation, dog, doll, doll carriage, dolt, donkey,
   dope, double take, drag, dragging, drawback, drive back, drop,
   dullard, dumb cluck, dumbbell, dummy, dummy share, dunce, eclipse,
   electric chair, eliminate, ell, embolism, embolus, enclave,
   engravement, engraving, erase, etching, even lot, exclude,
   extension, fend, fend off, field, fill, fill up, film,
   flight of ideas, forty, foul, fractional lot, freeze, full lot,
   gallows, gallows-tree, gas chamber, gewgaw, gibbet, gimcrack, gob,
   golf club, gorge, gowk, graphotype, guillotine, hallucination,
   hallucinosis, halt, halter, hamper, hang-up, hazard, hemp,
   hempen collar, hinder, hindrance, hitch, hobbyhorse, hold at bay,
   hold back, hold off, hold up, holding, holdings, holdup, hood,
   hot seat, hunk, hurdle, impasse, impede, impediment, impress,
   impression, imprint, infarct, infarction, inhibition, interim,
   jack-in-the-box, jacks, jackstones, jackstraws, jam, jobbernowl,
   joker, keep at bay, keep back, keep off, kickshaw, kit, knickknack,
   knot, kraal, lackwit, lag, lagging, lamebrain, lay on, lay out,
   lay over, lethal chamber, lightweight, linoleum-block print,
   lithograph, loaf, lock, logjam, looby, loon, lot, lump, maiden,
   make late, mantle, marble, marionette, mask, mass, mental block,
   mental confusion, mezzotint, mig, moratorium, muffle, negative,
   niais, nihilism, nihilistic delusion, nincompoop, ninny,
   ninnyhammer, nitwit, noddy, node, noose, nugget, obduce, objection,
   obscure, obstacle, obstipate, obstipation, obstruct, obstruction,
   obstructive, occlude, occult, odd lot, one small difficulty,
   outcry, outfit, outline, overlay, overspread, pack, pale,
   paper doll, paperasserie, paralogia, parcel of land, parry, pat,
   patch, pause, pick-up sticks, piece, pinwheel, plan, plat,
   plaything, plot, plot of ground, plug, plug up, preference share,
   prevent, print, psychological block, pull up, puppet, push back,
   put, put back, put on, put paid to, quad, quadrangle, quantity,
   racket, rag doll, real estate, rebuff, red tape, red-tapeism,
   red-tapery, repel, repression, reprieve, repulse, resistance,
   respite, restraint, retard, retardance, retardation, roadblock,
   rocking horse, rope, rough out, round lot, rub, rubber-block print,
   scaffold, screen, scum, sealing off, section, series, set, share,
   shield, shut off, shut out, shut tight, sketch, slab, slacken,
   slow down, slow-up, slowdown, slowness, snag, solid, solid body,
   spile, sport, spread over, square, squeeze, squeeze shut, stake,
   stalemate, stall, stanch, stave off, stay, stay of execution,
   steelie, stem, stem the tide, stench, stifle, stockholding,
   stockholdings, stop, stop cold, stop dead, stop short, stop up,
   stoppage, stopper, stopple, strangle, strangulate, strangulation,
   stuff, stuff up, stumbling block, stumbling stone, stump, stupid,
   stymie, sublimation, suffocate, suit, suite, superimpose,
   superpose, suppression, suspension, symbolization, taw, teetotum,
   the chair, thickwit, tie-up, time lag, top, toy, toy soldier,
   tract, tree, trinket, turn aside, veil, vendue, vignette, wad,
   wait, wall, ward off, whim-wham, wing, witling, wood engraving,
   woodblock, woodcut, woodprint, xylograph



The Jargon File (version 4.4.7, 29 Dec 2003):

block
 v.

    [common; from process scheduling terminology in OS theory]

    1. vi. To delay or sit idle while waiting for something. ?We're blocking
    until everyone gets here.? Compare busy-wait.

    2. block on vt. To block, waiting for (something). ?Lunch is blocked on
    Phil's arrival.?


The Free On-line Dictionary of Computing (30 December 2018):

block

   1.  A unit of data or memory, often, but not
   exclusively, on a magnetic disk or magnetic tape.

   Compare record, sector.

   (2000-07-17)

   2.  To delay or sit idle while waiting for
   something.

   Compare busy-wait.

   (2000-07-17)

   3.  A delimited section of source code in a
   block-structured language.

   (2004-09-29)