hour has 4 distinct synonyms spread across 3 of its 4 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 period of time equal to 1/24th of a day
“the job will take more than an hour”
clock time
“the hour is getting late”
Synonyms, antonyms and the broader and narrower relations for hour come from Princeton University’s WordNet. Full sources and licences.
a special and memorable period
“it was their finest hour”