Source : Webster's Revised Unabridged Dictionary (1913)

Plump \Plump\, a.
   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.

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

         To visit islands and the plumps of men.  --Chapman.

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.

   2. To drop or fall suddenly or heavily, all at
      once.``Dulcissa plumps into a chair.'' --Spectator.

   3. To {give} a plumper. See {Plumper}, 2.

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.

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

         The god of wine did his plump clusters bring. --T.
                                                  Carew.

Plump \Plump\, adv. [Cf. D. plomp, interj., G. plump, plumps.
   Cf. {Plump}, a. & v.]
   Directly; suddenly; perpendicularly. ``Fall plump.'' --Beau.
   & Fl.

Source : WordNet®

plump
     n : the sound of a sudden heavy fall

plump
     adv : straight down especially heavily or abruptly; "the anchor
           fell plump into the sea"; "we dropped the rock plump
           into the water"

plump
     adj : euphemisms for slightly fat; "a generation ago...buxom
           actresses were popular"- Robt.A.Hamilton; "chubby
           babies"; "pleasingly plump" [syn: {buxom}, {chubby}, {embonpoint},
            {zaftig}, {zoftig}]

plump
     v 1: drop sharply; "The stock market plummeted" [syn: {plummet}]
     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}]
     3: make fat or plump; "We will plump out that poor starving
        child" [syn: {fatten}, {fat}, {flesh out}, {fill out}, {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: {go}]