resignation 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.
the act of giving up (a claim or office or possession etc.)
a formal document giving notice of your intention to resign
“he submitted his resignation as of next month”
Synonyms, antonyms and the broader and narrower relations for resignation come from Princeton University’s WordNet. Full sources and licences.