/ Dictionary / Index H holy mackerel: Meaning and Definition of Find definitions for: ho'ly mack'erel Pronunciation: [key] — Slang. Slang. (used as an exclamation to express surprise or wonder.) Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Holy Land holy moly Related Content Daily Word Quiz: resilient Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language