spell has 14 distinct synonyms spread across 7 of its 10 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 one recorded opposite is unspell.
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 psychological state induced by (or as if induced by) a magical incantation
a time period for working (after which you will be relieved by someone else)
“it's my go”
Synonyms, antonyms and the broader and narrower relations for spell come from Princeton University’s WordNet. Full sources and licences.
a verbal formula believed to have magical force
“he whispered a spell as he moved his hands”