Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
untransmutable is an adjective meaning "not capable of being changed into something else". It carries one recorded sense.
not capable of being changed into something else
“the alchemists were unable to accept the inconvertible nature of elemental metals”
Definitions, synonyms and semantic relations for untransmutable come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.