mess has 25 distinct synonyms spread across 5 of its 8 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.
informal terms for a difficult situation
“he got into a terrible fix”
soft semiliquid food
“a mess of porridge”
a meal eaten in a mess hall by service personnel
a (large) military dining room where service personnel eat or relax
Synonyms, antonyms and the broader and narrower relations for mess come from Princeton University’s WordNet. Full sources and licences.