unintelligibility has 2 distinct synonyms 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 intelligibility.
nonsense that is simply incoherent and unintelligible
incomprehensibility as a consequence of being unintelligible
Synonyms, antonyms and the broader and narrower relations for unintelligibility come from Princeton University’s WordNet. Full sources and licences.
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.