rest has 25 distinct synonyms spread across 10 of its 18 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 be active.
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.
take a short break from one's activities in order to relax
put something in a resting position, as for support or steadying
“Rest your head on my shoulder”
be inactive, refrain from acting
“The committee is resting over the summer”
freedom from activity (work or strain or responsibility)
“took his repose by the swimming pool”
a pause for relaxation
“people actually accomplish more when they take time for short rests”
a state of inaction
“a body will continue in a state of rest until acted upon”
euphemisms for death (based on an analogy between lying in a bed and in a tomb)
“she was laid to rest beside her husband”
a musical notation indicating a silence of a specified duration
Synonyms, antonyms and the broader and narrower relations for rest come from Princeton University’s WordNet. Full sources and licences.