reversal has 14 distinct synonyms spread across 6 of its 8 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 affirmation.
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 change from one state to the opposite state
“there was a reversal of autonomic function”
turning in an opposite direction or position
“the reversal of the image in the lens”
a decision to reverse an earlier decision
a judgment by a higher court that the judgment of a lower court was incorrect and should be set aside
turning in the opposite direction
a major change in attitude or principle or point of view
“an about-face on foreign policy”
Synonyms, antonyms and the broader and narrower relations for reversal come from Princeton University’s WordNet. Full sources and licences.