unsaturated has no recorded synonym. 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 saturated.
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.
not saturated; capable of dissolving more of a substance at a given temperature
“an unsaturated salt solution”
used of a compound (especially of carbon) containing atoms sharing more than one valence bond
“unsaturated fats”
(of color) not chromatically pure; diluted
“an unsaturated red”
Synonyms, antonyms and the broader and narrower relations for unsaturated come from Princeton University’s WordNet. Full sources and licences.