slop has 15 distinct synonyms spread across 6 of its 9 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. WordNet records no antonym for it — antonymy is a relation between word forms rather than concepts, so it is deliberately sparse.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
(usually plural) waste water from a kitchen or bathroom or chamber pot that has to be emptied by hand
“she carried out the sink slops”
(usually plural) weak or watery unappetizing food or drink
“he lived on the thin slops that food kitchens provided”
writing or music that is excessively sweet and sentimental
Synonyms, antonyms and the broader and narrower relations for slop come from Princeton University’s WordNet. Full sources and licences.
ladle clumsily
“slop the food onto the plate”