sleeping has 4 distinct synonyms spread across 2 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 one recorded opposite is waking.
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.
quiet and inactive restfulness
Synonyms, antonyms and the broader and narrower relations for sleeping come from Princeton University’s WordNet. Full sources and licences.
the suspension of consciousness and decrease in metabolic rate
lying with head on paws as if sleeping