forget has 5 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. Its 2 recorded opposites are remember, mind.
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.
be unable to remember
“I'm drawing a blank”
Synonyms, antonyms and the broader and narrower relations for forget come from Princeton University’s WordNet. Full sources and licences.