Muck meaning : (slimy) mud, sludge. Soft (or slimy) manure. Anything filthy or vile. Dirt; something that makes another thing dirty. Grub, slop, swill Money The pile of discarded cards. To shovel muck. To manure with muck. To do a dirty job. To pass, to fold without showing one's cards, often done when a better hand has already been revealed.