cloud has 15 distinct synonyms spread across 5 of its 14 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.
make less visible or unclear
“The stars are obscured by the clouds”
billow up in the form of a cloud
“The smoke clouded above the houses”
make gloomy or depressed
“Their faces were clouded with sadness”
make less clear
“the stroke clouded memories of her youth”
make milky or dull
“The chemical clouded the liquid to which it was added”
any collection of particles (e.g., smoke or dust) or gases that is visible
Synonyms, antonyms and the broader and narrower relations for cloud come from Princeton University’s WordNet. Full sources and licences.
a visible mass of water or ice particles suspended at a considerable altitude
out of touch with reality
“his head was in the clouds”
a cause of worry or gloom or trouble
“the only cloud on the horizon was the possibility of dissent by the French”
suspicion affecting your reputation
“after that mistake he was under a cloud”
a group of many things in the air or on the ground
“a swarm of insects obscured the light”