Meaning

noun wet feed (especially for pigs) consisting of mostly kitchen waste mixed with water or skimmed or sour milk

noun deep soft mud in water or slush

noun (usually plural) waste water from a kitchen or bathroom or chamber pot that has to be emptied by hand

originEtymology tree Old English *sloppe Middle English *sloppe? English slop Probably from Middle English *sloppe (attested in plural form sloppes), representing Old English *sloppe (attested in cūsloppe), alternative form of Old English slyppe. Related to slip. (Internet slang) Possibly a backformation from goyslop.

Etymology from Wiktionary, CC BY-SA 3.0