
Define muck: soft moist farmyard manure; slimy dirt or filth; defamatory remarks or writings — muck in a sentence. midc., "cow dung and vegetable matter spread as manure," from a Scandinavian source, cf. Old Norse myki, mykr "cow dung," Danish møg, from. Define muck. muck synonyms, muck pronunciation, muck translation, English dictionary definition of muck. n. 1. A moist sticky mixture, especially of mud and filth.