The Collaborative International Dictionary of English v.0.48:

Scour \Scour\, v. i.
   1. To clean anything by rubbing. --Shak.
      [1913 Webster]

   2. To cleanse anything.
      [1913 Webster]

            Warm water is softer than cold, for it scoureth
            better.                               --Bacon.
      [1913 Webster]

   3. To be purged freely; to have a diarrhoea.
      [1913 Webster]

   4. To run swiftly; to rove or range in pursuit or search of
      something; to scamper.
      [1913 Webster]

            So four fierce coursers, starting to the race,
            Scour through the plain, and lengthen every pace.
                                                  --Dryden.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Scour \Scour\ (skour), v. t. [imp. & p. p. Scoured; p. pr. &
   vb. n. Scouring.] [Akin to LG. sch["u]ren, D. schuren,
   schueren, G. scheuern, Dan. skure; Sw. skura; all possibly
   fr. LL. escurare, fr. L. ex + curare to take care. Cf.
   Cure.]
   1. To rub hard with something rough, as sand or Bristol
      brick, especially for the purpose of cleaning; to clean by
      friction; to make clean or bright; to cleanse from grease,
      dirt, etc., as articles of dress.
      [1913 Webster]

   2. To purge; as, to scour a horse.
      [1913 Webster]

   3. To remove by rubbing or cleansing; to sweep along or off;
      to carry away or remove, as by a current of water; --
      often with off or away.
      [1913 Webster]

            [I will] stain my favors in a bloody mask,
            Which, washed away, shall scour my shame with it.
                                                  --Shak.
      [1913 Webster]

   4. [Perhaps a different word; cf. OF. escorre, escourre, It.
      scorrere, both fr. L. excurrere to run forth. Cf.
      Excursion.] To pass swiftly over; to brush along; to
      traverse or search thoroughly; as, to scour the coast.
      [1913 Webster]

            Not so when swift Camilla scours the plain. --Pope.
      [1913 Webster]

   5. To cleanse or clear, as by a current of water; to flush.

            If my neighbor ought to scour a ditch. --Blackstone.
      [Webster 1913 Suppl.]

   Scouring barrel, a tumbling barrel. See under Tumbling.


   Scouring cinder (Metal.), a basic slag, which attacks the
      lining of a shaft furnace. --Raymond.

   Scouring rush. (Bot.) See Dutch rush, under Dutch.

   Scouring stock (Woolen Manuf.), a kind of fulling mill.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Scour \Scour\, n.
   1. Diarrhoea or dysentery among cattle.
      [1913 Webster]

   2. The act of scouring.
      [Webster 1913 Suppl.]

   3. A place scoured out by running water, as in the bed of a
      stream below a fall.

            If you catch the two sole denizens [trout] of a
            particular scour, you will find another pair
            installed in their place to-morrow.   --Grant Allen.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

scour
    n 1: a place that is scoured (especially by running water)
    v 1: examine minutely; "The police scoured the country for the
         fugitive"
    2: clean with hard rubbing; "She scrubbed his back" [syn:
       scrub, scour]
    3: rub hard or scrub; "scour the counter tops" [syn: scour,
       abrade]
    4: rinse, clean, or empty with a liquid; "flush the wound with
       antibiotics"; "purge the old gas tank" [syn: flush,
       scour, purge]

Moby Thesaurus II by Grady Ward, 1.0:

190 Moby Thesaurus words for "scour":
   ablate, abrade, abrase, baptize, bark, bath, bathe, beat,
   beat the bushes, beeline, bite, blow, blow out, bolt, buff, bullet,
   burnish, career, chafe, clean, clean out, cleanse, clear,
   clear away, clear off, clear out, clear the decks, comb, corrode,
   course, cover, dart, dash, defecate, deplete, do, douche, drain,
   eat, eat away, eliminate, empty, empty out, erase, erode, evacuate,
   exhaust, fan, ferret out, file, find, finish, fleet, fling, flit,
   flush, flush out, fly, forage, fray, frazzle, fret, furbish, gall,
   gargle, glance, glaze, gloss, gnaw, gnaw away, go over, grate,
   graze, grind, grub, haste, hasten, hie, highball, holystone, hump,
   hump it, hurry, hurtle, irrigate, lather, launder, lave, look,
   look all over, look everywhere, look for, luster, make haste,
   measure, mop, mop up, overpass, pass over, pass through, patrol,
   perambulate, peregrinate, pererrate, ply, polish, post, purge,
   race, rake, range, range over, ransack, rasp, raze, reconnoiter,
   remove, rifle, rinse, rinse out, ritually immerse, rocket, rout,
   rub, rub away, rub off, rub out, rummage, rush, scamper, scoot,
   scour out, scour the country, scout, scramble, scrape, scrub,
   scrub up, scud, scuff, scurry, scuttle, search, search high heaven,
   seek, shake, shake down, shampoo, shine, shoot, shower, skedaddle,
   skin, sleek, slick, slick down, sluice, sluice out, smoke, soap,
   speed, sponge, step on it, swab, sweep, sweep out, syringe, tear,
   toivel, toss, track, transit, travel over, travel through,
   traverse, tub, turn inside out, turn upside down, unclog, unfoul,
   varnish, vent, void, voyage, wash, wash out, wash up, wax, wear,
   wear away