The Collaborative International Dictionary of English v.0.48:

Dig \Dig\, v. i.
   1. To work with a spade or other like implement; to do
      servile work; to delve.
      [1913 Webster]

            Dig for it more than for hid treasures. --Job iii.
                                                  21.
      [1913 Webster]

            I can not dig; to beg I am ashamed.   --Luke xvi. 3.
      [1913 Webster]

   2. (Mining) To take ore from its bed, in distinction from
      making excavations in search of ore.
      [1913 Webster]

   3. To work hard or drudge; specif. (U. S.): To study
      ploddingly and laboriously. [Colloq.]
      [Webster 1913 Suppl.]

            Peter dug at his books all the harder. --Paul L.
                                                  Ford.
      [Webster 1913 Suppl.]

   4. (Mach.) Of a tool: To cut deeply into the work because ill
      set, held at a wrong angle, or the like, as when a lathe
      tool is set too low and so sprung into the work.

   To dig out, to depart; to leave, esp. hastily; decamp.
      [Slang, U. S.]
      [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Dig \Dig\ (d[i^]g), v. t. [imp. & p. p. Dug (d[u^]g) or
   Digged (d[i^]gd); p. pr. & vb. n. Digging. -- Digged is
   archaic.] [OE. diggen, perh. the same word as diken, dichen
   (see Dike, Ditch); cf. Dan. dige to dig, dige a ditch; or
   (?) akin to E. 1st dag. [root]67.]
   1. To turn up, or delve in, (earth) with a spade or a hoe; to
      open, loosen, or break up (the soil) with a spade, or
      other sharp instrument; to pierce, open, or loosen, as if
      with a spade.
      [1913 Webster]

            Be first to dig the ground.           --Dryden.
      [1913 Webster]

   2. To get by digging; as, to dig potatoes, or gold.
      [1913 Webster]

   3. To hollow out, as a well; to form, as a ditch, by removing
      earth; to excavate; as, to dig a ditch or a well.
      [1913 Webster]

   4. To thrust; to poke. [Colloq.]
      [1913 Webster]

            You should have seen children . . . dig and push
            their mothers under the sides, saying thus to them:
            Look, mother, how great a lubber doth yet wear
            pearls.                               --Robynson
                                                  (More's
                                                  Utopia).
      [1913 Webster]

   5. To like; enjoy; admire. The whole class digs Pearl Jam.
      [Colloq.]
      [PJC]

   To dig down, to undermine and cause to fall by digging; as,
      to dig down a wall.

   To dig from, To dig out of, To dig out, To dig up, to
      get out or obtain by digging; as, to dig coal from or out
      of a mine; to dig out fossils; to dig up a tree. The
      preposition is often omitted; as, the men are digging
      coal, digging iron ore, digging potatoes.

   To dig in,
      (a) to cover by digging; as, to dig in manure.
      (b) To entrench oneself so as to give stronger resistance;
          -- used of warfare or negotiating situations.

   to dig in one's heels To offer stubborn resistance.
      [1913 Webster +PJC]

The Collaborative International Dictionary of English v.0.48:

dig \dig\ (d[i^]g), v. t.
   1. To understand; as, do you dig me?. [slang]
      [PJC]

   2. To notice; to look at; as, dig that crazy hat!. [slang]
      [PJC]

   3. To appreciate and enjoy; as, he digs classical music as
      well as rock. [slang]
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Dig \Dig\, n.
   1. A thrust; a punch; a poke; as, a dig in the side or the
      ribs. See Dig, v. t., 4. [Colloq.]
      [1913 Webster]

   2. A plodding and laborious student. [Cant, U.S.]
      [1913 Webster]

   3. A tool for digging. [Dial. Eng.]
      [Webster 1913 Suppl.]

   4. An act of digging.
      [Webster 1913 Suppl.]

   5. An amount to be dug.
      [Webster 1913 Suppl.]

   6. (Mining) same as Gouge.
      [Webster 1913 Suppl.]

   7. a critical and sometimes sarcastic or insulting remark,
      but often good-humored; as, celebrities at a roast must
      suffer through countless digs.
      [PJC]

   8. An archeological excavation site.
      [PJC]

WordNet (r) 3.0 (2006):

dig
    n 1: the site of an archeological exploration; "they set up camp
         next to the dig" [syn: dig, excavation, archeological
         site]
    2: an aggressive remark directed at a person like a missile and
       intended to have a telling effect; "his parting shot was
       `drop dead'"; "she threw shafts of sarcasm"; "she takes a dig
       at me every chance she gets" [syn: shot, shaft, slam,
       dig, barb, jibe, gibe]
    3: a small gouge (as in the cover of a book); "the book was in
       good condition except for a dig in the back cover"
    4: the act of digging; "there's an interesting excavation going
       on near Princeton" [syn: excavation, digging, dig]
    5: the act of touching someone suddenly with your finger or
       elbow; "she gave me a sharp dig in the ribs" [syn: dig,
       jab]
    v 1: turn up, loosen, or remove earth; "Dig we must"; "turn over
         the soil for aeration" [syn: dig, delve, cut into,
         turn over]
    2: create by digging; "dig a hole"; "dig out a channel" [syn:
       dig, dig out]
    3: work hard; "She was digging away at her math homework";
       "Lexicographers drudge all day long" [syn: labor, labour,
       toil, fag, travail, grind, drudge, dig, moil]
    4: remove, harvest, or recover by digging; "dig salt"; "dig
       coal" [syn: dig, dig up, dig out]
    5: thrust down or into; "dig the oars into the water"; "dig your
       foot into the floor"
    6: remove the inner part or the core of; "the mining company
       wants to excavate the hillside" [syn: excavate, dig,
       hollow]
    7: poke or thrust abruptly; "he jabbed his finger into her ribs"
       [syn: jab, prod, stab, poke, dig]
    8: get the meaning of something; "Do you comprehend the meaning
       of this letter?" [syn: grok, get the picture,
       comprehend, savvy, dig, grasp, compass,
       apprehend]

Moby Thesaurus II by Grady Ward, 1.0:

317 Moby Thesaurus words for "dig":
   Parthian shot, abide, absorb, abysm, abyss, accept, appreciate,
   apprehend, assault, assimilate, back answer, backset, bang, bash,
   bat, be affected, be in tune, be inspired, be involved, be moved,
   be with one, bear, bear upon, bearing, beat the bushes, beating,
   belt, bide, biff, blow, bone, bonk, boost, bore, bring in, buck,
   bull, bulldoze, bump, bump against, bunt, burrow, butt,
   butt against, care about, catch, catch on, catch the flame,
   catch the infection, caustic remark, change color, chasm, chop,
   clip, clout, clump, color with emotion, comeback, comprehend, con,
   conceive, contemplate, countersink, crack, cram, crop, crop herbs,
   crowd, cultivate, culture, cut, cutting remark, dash, deepen,
   delve, depress, dig out, dig up, digest, diggings, dike, dint,
   dive, dredge, dress, drill, drive, drub, drubbing, drudge,
   drumming, dump, dwell, echo, elbow, elucubrate, empathize with,
   enter, examine, excavate, excavation, explore, fag, fallow, fathom,
   fertilize, fleer, flout, follow, foolery, forage, force, frisk,
   furrow, fusillade, gather, gather in, get, get hold of,
   get the drift, get the idea, get the picture, gibe, gibing retort,
   glean, go, go over, go through, goad, gouge, gouge out, grabble,
   grasp, grind, groove, grub, gulf, hammer, hammer away, hang out,
   harrow, harvest, have, have it taped, hay, head, hit, hoe, hunt,
   hurtle, hustle, identify with, jab, jam, jape, jeer, jest, jog,
   joggle, jolt, jostle, ken, knock, know, learn, leg-pull, lick,
   like, list, live, look around, look round, look through, lower,
   lucubrate, master, mind, mine, mock, moil, mow, mulch, nose around,
   nudge, nut, parting shot, peg, peg away, pelt, penetrate, peruse,
   pick, pierce, pile drive, pit, plod, plow, pluck, plug, plug along,
   plug away, plunge, plunge into, plunk, poke, poke around,
   pore over, pound, pound away, practice, press, pressure, probe,
   prod, prune, pry, punch, push, put-down, put-on, quarry, quip,
   rake, ram, ram down, rap, rattle, react, read, realize, reap,
   reap and carry, regard studiously, relate to emotionally, relish,
   research, respond, restudy, review, root, root out, rude reproach,
   run, run against, sap, savvy, scoff, scoop, scoop out, scrabble,
   scrape, scratch, scurrility, search, search through, see, seize,
   seize the meaning, sense, shaft, shake, share, short answer,
   shoulder, shove, shovel, sink, slam, slap, slog, slug, smack,
   smash, smell around, sock, spade, stab, stick, stress, stroke,
   study, swat, swing, swipe, swot, sympathize with, take, take in,
   tamp, tattoo, taunt, thin, thin out, thrust, thump, thwack, till,
   till the soil, toil, travail, trench, trough, tunnel, twit,
   understand, verbal thrust, vet, wade through, weed, weed out, well,
   whack, whop, work, work away, workings, yerk