Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
unauthorised is an adjective meaning "not endowed with authority". It carries 2 recorded senses.
not endowed with authority
without official authorization
“an unauthorized strike”
“wildcat work stoppage”
Definitions, synonyms and semantic relations for unauthorised come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.