/ Dictionary / Index P pump gun: Meaning and Definition of Find definitions for: pump' gun" Pronunciation: [key] a shotgun or rifle having a pump-action mechanism. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. pumpernickel pumping Related Content Daily Word Quiz: penchant Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language