Definitions of plump:

• noun:   the sound of a sudden heavy fall
• verb:   give support (to) or make a choice (of) one out of a group or number

  Example: "I plumped for the losing candidates"

• verb:   drop sharply
• verb:   make fat or plump

  Example: "We will plump out that poor starving child"

• verb:   set (something or oneself) down with or as if with a noise
• adjective:   euphemisms for slightly fat

  Example: "Pleasingly plump"

• adverb:   straight down especially heavily or abruptly

  Example: "The anchor fell plump into the sea"

• name:  A surname (very rare: popularity rank in the U.S.: #21326)