The Collaborative International Dictionary of English v.0.48:

Plump \Plump\, n.
   A knot; a cluster; a group; a crowd; a flock; as, a plump of
   trees, fowls, or spears. [Obs.]
   [1913 Webster]

         To visit islands and the plumps of men.  --Chapman.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Plump \Plump\, v. i. [Cf. D. plompen, G. plumpen, Sw. plumpa,
   Dan. plumpe. See Plump, a.]
   1. To grow plump; to swell out; as, her cheeks have plumped.
      [1913 Webster]

   2. To drop or fall suddenly or heavily, all at once."Dulcissa
      plumps into a chair." --Spectator.
      [1913 Webster]

   3. To give a plumper. See Plumper, 2.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Plump \Plump\, v. t. [imp. & p. p. Plumped; p. pr. & vb. n.
   Plumping.]
   1. To make plump; to fill (out) or support; -- often with up.
      [1913 Webster]

            To plump up the hollowness of their history with
            improbable miracles.                  --Fuller.
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   2. To cast or let drop all at once, suddenly and heavily; as,
      to plump a stone into water.
      [1913 Webster]

   3. To give (a vote), as a plumper. See Plumper, 2.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Plump \Plump\ (pl[u^]mp), a. [Compar. Plumper
   (pl[u^]mp"[~e]r); superl. Plumpest.] [OE. plomp rude,
   clumsy; akin to D. plomp, G., Dan., & Sw. plump; probably of
   imitative origin. Cf. Plump, adv.]
   1. Well rounded or filled out; full; fleshy; fat; as, a plump
      baby; plump cheeks. --Shak.
      [1913 Webster]

            The god of wine did his plump clusters bring. --T.
                                                  Carew.
      [1913 Webster]

   2. Done or made plump, or suddenly and without reservation;
      blunt; unreserved; direct; downright.

            After the plump statement that the author was at
            Erceldoune and spake with Thomas.     --Saintsbury.
      [Webster 1913 Suppl.]

The Collaborative International Dictionary of English v.0.48:

Plump \Plump\, adv. [Cf. D. plomp, interj., G. plump, plumps.
   Cf. Plump, a. & v.]
   Directly; suddenly; perpendicularly. "Fall plump." --Beau. &
   Fl.
   [1913 Webster]

WordNet (r) 3.0 (2006):

plump
    adv 1: straight down especially heavily or abruptly; "the anchor
           fell plump into the sea"; "we dropped the rock plump into
           the water"
    adj 1: sufficiently fat so as to have a pleasing fullness of
           figure; "a chubby child"; "pleasingly plump"; [syn:
           chubby, embonpoint, plump]
    n 1: the sound of a sudden heavy fall
    v 1: drop sharply; "The stock market plummeted" [syn: plummet,
         plump]
    2: set (something or oneself) down with or as if with a noise;
       "He planked the money on the table"; "He planked himself into
       the sofa" [syn: plank, flump, plonk, plop, plunk,
       plump down, plunk down, plump]
    3: make fat or plump; "We will plump out that poor starving
       child" [syn: fatten, fat, flesh out, fill out,
       plump, plump out, fatten out, fatten up]
    4: give support (to) or make a choice (of) one out of a group or
       number; "I plumped for the losing candidates" [syn: plump,
       go]

Moby Thesaurus II by Grady Ward, 1.0:

233 Moby Thesaurus words for "plump":
   abruptly, adipose, ample, at once, back, ballot, bang, beamy,
   become overweight, beefy, big-bellied, bloated, blowzy, blunt,
   bosomy, brawny, bump, burly, busty, buxom, campaign for, canvass,
   cast, cast a ballot, cave, cave in, chink, choose, chubby, chuck,
   chunky, clap, click, clink, clop, clump, clunk, collapse,
   corpulent, crump, cushion, dash, decline, definite, definitive,
   deposit, direct, directly, distended, dive, divide, downright,
   droop, drop, dull thud, dumpy, ease, engross, exactly, fall, fat,
   fatten, fattish, fleshy, flick, fling, flop, flop down, fluff,
   flump, flump down, flush, forthright, founder, full, full-bodied,
   gain weight, gather flesh, gentle, give way, go down, gross,
   hastily, heavyset, hefty, hippy, hurl, impetuously, imposing,
   impulsively, kerplunk, knead, lapse, laxate, like a flash,
   like a thunderbolt, limber, limber up, loosen, lower, lusty, mash,
   massage, matter-of-fact, meaty, mellow, milden, mollify, nose-dive,
   obese, of a sudden, on short notice, overweight, pad, parachute,
   pat, patter, paunchy, pinguefy, pitapat, pitch, pitter-patter,
   plain, plank, plop, plop down, plumb, plummet, plunge, plunk,
   podgy, point-blank, poll, pop, portly, potbellied, pounce,
   pounce on, pounce upon, precipitantly, precipitately,
   precipitously, precisely, pudgy, puff up, puffy, pulp, pursy,
   put down, put on weight, rap, relax, right, roly-poly, rotund,
   round, roundabout, sag, select, set, set down, settle, settle down,
   shake up, sharp, side with, simple, sink, sink down, skin-dive,
   sky-dive, slap, slouch, slump, slump down, smack, smack-dab, smash,
   soften, soften up, sound, spang, square, squarely, squash, squat,
   squatty, stalwart, startlingly, steatopygous, stocky, stoop, stout,
   straight, strapping, subdue, submerge, subside, sudden, suddenly,
   supple, support, surprisingly, swag, swollen, swoop, swoop down,
   take a header, tap, tenderize, thick-bodied, thickset, throw,
   thrust, thud, thump, tick, tinkle, tone down, top-heavy, toss,
   tubby, tune down, tunk, unambiguous, unawares, unequivocal,
   unexpectedly, unmistakable, vote, well-fed, without notice,
   without warning