What does "plump" mean?

Additional senses

1. 2.To drop or fall suddenly or heavily, all at once."Dulcissa plumps into a chair." Spectator.
2. 3.To give a plumper. See Plumper, 2.
3. 4.To make plump; to fill (out) or support; -- often with up.plump up the pillows To plump up the hollowness of their history with improbable miracles. Fuller.
4. 5.To cast or let drop all at once, suddenly and heavily; as, to plump a stone into water.
5. 6.To give (a vote), as a plumper. See Plumper, 2.
6. 7.Directly; suddenly; perpendicularly. "Fall plump." Beau. & Fl.