Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
unfaithfully is an adverb meaning "in an unfaithful undependable unreliable manner". It carries one recorded sense.
in an unfaithful undependable unreliable manner
Definitions, synonyms and semantic relations for unfaithfully come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.