/ Dictionary / Index G gabbro: Meaning and Definition of Find definitions for: gab•bro Pronunciation: (gab'rō), [key] — pl. -bros. a dark granular igneous rock composed essentially of labradorite and augite. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: gabbro (Thesaurus) gabble gabby Related Content Daily Word Quiz: endear Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language