/ Dictionary / Index G giga-: Meaning and Definition of Find definitions for: giga- Pronunciation: [key] a combining form meaning “billion,” used in the formation of compound words: gigabyte. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. gig gigabit Related Content Daily Word Quiz: crutiny Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language