exercise has 19 distinct synonyms spread across 9 of its 11 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 activity of exerting your muscles in various ways to keep fit
“the doctor recommended regular exercise”
systematic training by multiple repetitions
“practice makes perfect”
(usually plural) a ceremony that involves processions and speeches
“academic exercises”
an action, often used negatively and without consequences
“an exercise in futility”
Synonyms, antonyms and the broader and narrower relations for exercise come from Princeton University’s WordNet. Full sources and licences.