verb

• (intransitive) To grow plump; to swell out.
  "Her cheeks have plumped."
• (transitive) To make plump; to fill (out) or support; often with up.
  "to plump oysters or scallops by placing them in fresh or brackish water"
• (intransitive) To give a plumper (kind of vote).
• (transitive) To give (a vote), as a plumper.

verb

• (transitive) To cast or let drop (something) all at once, suddenly and heavily.
  "to plump a stone into water"
• (intransitive) To drop or fall suddenly or heavily, all at once.
  "September 24, 1712, The Spectator No. 492, letter from a prude Dulcissa plumps into a chair."

noun

• (obsolete) A knot or cluster; a group; a crowd.
  "a plump of trees, fowls, or spears"