canteen has 1 distinct synonym spread across 1 of its 5 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.
a flask for carrying water; used by soldiers or travelers
sells food and personal items to personnel at an institution or school or camp etc.
a restaurant outside; often for soldiers or policemen
Synonyms, antonyms and the broader and narrower relations for canteen come from Princeton University’s WordNet. Full sources and licences.
a recreation room in an institution
restaurant in a factory; where workers can eat