Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
nonassertive is an adjective meaning "not aggressively self-assured, though not necessarily lacking in confidence". It carries one recorded sense.
not aggressively self-assured, though not necessarily lacking in confidence
“she was quiet and nonassertive as she took control”
Definitions, synonyms and semantic relations for nonassertive come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.