day of atonement has 1 distinct synonym spread across 1 of its 1 sense. 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.
(Judaism) a solemn and major fast day on the Jewish calendar; 10th of Tishri; its observance is one of the requirements of the Mosaic law
Synonyms, antonyms and the broader and narrower relations for day of atonement come from Princeton University’s WordNet. Full sources and licences.