WordNet sense 1 (make or move along with a sound as of a horse's hooves striking the ground):

clop, clump, clunk

WordNet sense 2 (drop steeply):

dive, plunge

WordNet sense 3 (set (something or oneself) down with or as if with a noise):

plank, plop, plump, flump, plonk, plump down, plunk down

WordNet sense 4 (pull lightly but sharply with a plucking motion):

pick, pluck

WordNet sense 5 ((baseball) hitting a baseball so that it drops suddenly):

plunker