The Collaborative International Dictionary of English v.0.48:

Thump \Thump\, n. [Probably of imitative origin; perhaps
   influenced by dump, v. t.]
   1. The sound made by the sudden fall or blow of a heavy body,
      as of a hammer, or the like.
      [1913 Webster]

            The distant forge's swinging thump profound.
                                                  --Wordsworth.
      [1913 Webster]

            With heavy thump, a lifeless lump,
            They dropped down, one by one.        --Coleridge.
      [1913 Webster]

   2. A blow or knock, as with something blunt or heavy; a heavy
      fall.
      [1913 Webster]

            The watchman gave so great a thump at my door, that
            I awaked at the knock.                --Tatler.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Thump \Thump\, v. t. [imp. & p. p. Thumped; p. pr. & vb. n.
   Thumping.]
   To strike or beat with something thick or heavy, or so as to
   cause a dull sound.
   [1913 Webster]

         These bastard Bretons; whom our hathers
         Have in their own land beaten, bobbed, and thumped.
                                                  --Shak.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Thump \Thump\, v. i.
   To give a thump or thumps; to strike or fall with a heavy
   blow; to pound.
   [1913 Webster]

         A watchman at midnight thumps with his pole. --Swift.
   [1913 Webster]

WordNet (r) 3.0 (2006):

thump
    n 1: a heavy dull sound (as made by impact of heavy objects)
         [syn: thump, thumping, clump, clunk, thud]
    2: a heavy blow with the hand
    v 1: move rhythmically; "Her heart was beating fast" [syn:
         beat, pound, thump]
    2: make a dull sound; "the knocker thudded against the front
       door" [syn: thud, thump]
    3: hit hard with the hand, fist, or some heavy instrument; "the
       salesman pounded the door knocker"; "a bible-thumping
       Southern Baptist" [syn: thump, pound, poke]

Moby Thesaurus II by Grady Ward, 1.0:

156 Moby Thesaurus words for "thump":
   bang, bash, baste, bastinado, bat, batter, beat, beat a ruffle,
   beat a tattoo, beat the drum, beat time, beating, belabor, belt,
   biff, birch, blow, bonk, buffet, bump, cane, chink, chop, clap,
   click, clink, clip, clobber, clop, clout, club, clump, clunk,
   coldcock, count, count the beats, cowhide, crack, crump, cudgel,
   cut, dash, deal, deal a blow, deck, dig, dint, drub, drubbing,
   drum, drumming, dull thud, fetch, fetch a blow, flagellate, flail,
   flap, flick, flog, flump, flutter, fusillade, fustigate,
   give a whipping, give the stick, go pitapat, hammer, hit,
   hit a clip, horsewhip, jab, keep time, knock, knock cold,
   knock down, knock out, knout, lace, lambaste, larrup, lash, lay on,
   let have it, lick, maul, pad, palpitate, paste, pat, patter, pelt,
   pistol-whip, pitapat, pitter-patter, play drum, plump, plunk, poke,
   pommel, pop, pound, pulsate, pulverize, pummel, punch, rap,
   rawhide, roll, ruffle, scourge, slam, sledgehammer, slog, slug,
   smack, smash, smite, snap, soak, sock, sound a tattoo, spank,
   splatter, splutter, sputter, strap, strike, strike at, stripe,
   stroke, swat, swing, swinge, swipe, switch, tap, tattoo, thrash,
   thresh, throb, thrum, thud, thwack, tick, tinkle, tom-tom, trounce,
   truncheon, tunk, wallop, whack, whale, wham, whip, whop, yerk