/ Dictionary / Index P pump box: Meaning and Definition of Find definitions for: pump' box" Pronunciation: [key] a chamber of a pump in which a piston operates. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. pump-action pumper Related Content Daily Word Quiz: gregarious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language