adj. 1.euphemisms for slightly fat plump adv. 1.straight down especially heavily or abruptly plump n. 1.the sound of a sudden heavy fall plump v. 1.drop sharply 2.set (something or oneself) down with or as if with a noise 3.make fat or plump 4.give support (to) or make a choice (of) one out of a group or number