/ Dictionary / Index J jackhammer: Meaning and Definition of Find definitions for: jack•ham•mer Pronunciation: ( jak'ham"ur), [key] — n. a portable drill operated by compressed air and used to drill rock, break up pavement, etc. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: jackhammer (Thesaurus) jackfruit Jackie Related Content Daily Word Quiz: fabricate Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language