/ Dictionary / Index M muck-up: Meaning and Definition of Find definitions for: muck-up Pronunciation: (muk'up"), [key] — n. Informal. a bungled or disordered situation; foul-up. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: muck-up (Thesaurus) muckrake muckworm Related Content Daily Word Quiz: entomology Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language