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