The Collaborative International Dictionary of English v.0.48:

Clump \Clump\ (kl[u^]mp), n. [Cf. D. klomp lump, G. klump,
   klumpen, Dan. klump, Sw. klump; perh. akin to L. globus, E.
   globe. Cf. Club.]
   1. An unshaped piece or mass of wood or other substance.
      [1913 Webster]

   2. A cluster; a group; a thicket.
      [1913 Webster]

            A clump of shrubby trees.             --Hawthorne.
      [1913 Webster]

   3. The compressed clay of coal strata. --Brande & C.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Clump \Clump\, v. t.
   To arrange in a clump or clumps; to cluster; to group.
   --Blackmore.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Clump \Clump\, v. i.
   To tread clumsily; to clamp. [Prov. Eng.] --Halliwell.
   [1913 Webster]

WordNet (r) 3.0 (2006):

clump
    n 1: a grouping of a number of similar things; "a bunch of
         trees"; "a cluster of admirers" [syn: bunch, clump,
         cluster, clustering]
    2: a compact mass; "a ball of mud caught him on the shoulder"
       [syn: ball, clod, glob, lump, clump, chunk]
    3: a heavy dull sound (as made by impact of heavy objects) [syn:
       thump, thumping, clump, clunk, thud]
    v 1: make or move along with a sound as of a horse's hooves
         striking the ground [syn: clop, clump, clunk,
         plunk]
    2: come together as in a cluster or flock; "The poets
       constellate in this town every summer" [syn: cluster,
       constellate, flock, clump]
    3: walk clumsily [syn: clump, clomp]
    4: gather or cause to gather into a cluster; "She bunched her
       fingers into a fist" [syn: bunch, bunch up, bundle,
       cluster, clump]

Moby Thesaurus II by Grady Ward, 1.0:

327 Moby Thesaurus words for "clump":
   accumulate, agglomerate, aggregate, aggroup, amass, amble, array,
   assemble, bang, barge, bash, bat, batch, beating, belt, biff,
   bilge, blain, bleb, blister, blob, block, blow, body, bonk, boss,
   bow, bowl along, bring together, bubble, bulb, bulge, bulk, bulla,
   bump, bunch, bunch together, bunch up, bundle, burl, button, cahot,
   cake, chine, chink, chop, chunk, clabber, clap, click, clink, clip,
   clobber, clod, clop, clot, clout, clunk, cluster, clutter,
   coagulate, coldcock, collect, colligate, collocate, combine,
   compare, compile, concrete, concretion, condyle, congeal,
   conglomerate, conglomeration, convex, copse, corral, crack, crop,
   crump, cumulate, curd, curdle, cut, dash, deal, deal a blow, deck,
   dig, dig up, dint, dowel, drag, draw together, dredge up,
   drive together, drub, drubbing, drumming, dull thud, ear, fetch,
   fetch a blow, flange, flap, flick, flounce, flump, foot, footslog,
   fusillade, gall, gather, gather in, gather together, gel,
   gelatinate, gelatinize, get in, get together, gnarl, gob, group,
   grouping, groupment, grove, growth, halt, handle, hassock, heap,
   hill, hippety-hop, hit, hit a clip, hitch, hobble, hodgepodge, hop,
   hump, hunch, hunk, incrassate, inspissate, jab, jell, jellify,
   jelly, jog, joggle, join, jolt, jumble, jump, juxtapose, knob,
   knock, knock cold, knock down, knock out, knot, knur, knurl,
   let have it, lick, limp, lip, loaf, loop, lopper, lot, lumber,
   lump, lump together, lunge, lurch, make up, mass, match, mess,
   mince, mobilize, mole, mountain, muster, nevus, node, nub, nubbin,
   nubble, nugget, omnium-gatherum, pace, pad, paddle, pair,
   papilloma, parcel, partner, paste, pat, patter, peg, pelt, piaffe,
   piaffer, pile, pitapat, pitter-patter, plantation, planting, plod,
   plump, plunk, poke, pop, pound, prance, punch, put together,
   quantity, rack, raise, rake up, rally, rap, rib, ridge, ring, roll,
   round up, sashay, saunter, scrape together, scuff, scuffle,
   scuttle, set, shamble, shock, shoulder, shuffle, sidle,
   single-foot, skip, slam, slew, slink, slither, slog, slouch, slug,
   smack, smash, smite, snap, soak, sock, solid, solid body, spine,
   spinney, stagger, stalk, stamp, stand, stomp, stook, straddle,
   straggle, stride, strike, strike at, stroke, stroll, strut, stud,
   stumble, stump, style, swagger, swat, swing, swipe, tab, take up,
   tap, tattoo, thick, thicken, thicket, thud, thump, thwack, tick,
   tinkle, tittup, toddle, totter, traipse, trample, tread, trip,
   trudge, tubercle, tubercule, tuft, tunk, tussock, verruca, vesicle,
   wad, waddle, wale, wallop, wamble, wart, welt, whack, wham,
   whip in, whop, wiggle, wisp, wobble, wood, yerk