WordNet (r) 3.0 (2006):
plump down v 1: drop heavily [syn: plonk down, plump down, plank down] 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]