insolubility has 1 distinct synonym spread across 1 of its 2 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 solubility.
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.
the property (of a problem or difficulty) that makes it impossible to solve
the quality of being insoluble and difficult to dissolve in liquid
Synonyms, antonyms and the broader and narrower relations for insolubility come from Princeton University’s WordNet. Full sources and licences.