Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
unalterability is a noun meaning "the quality of not being alterable". It carries 2 recorded senses.
the quality of not being alterable
the quality of being fixed and unchangeable
“the fixedness of his gaze upset her”
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for unalterability come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.