waterloo has 1 distinct synonym spread across 1 of its 3 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 town in central Belgium where in 1815 Napoleon met his final defeat
a final crushing defeat
“he met his waterloo”
the battle on 18 June 1815 in which Prussian and British forces under Blucher and the Duke of Wellington routed the French forces under Napoleon
Synonyms, antonyms and the broader and narrower relations for waterloo come from Princeton University’s WordNet. Full sources and licences.