Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
self-assurance is a noun meaning "freedom from doubt; belief in yourself and your abilities". It carries one recorded sense.
freedom from doubt; belief in yourself and your abilities
“his assurance in his superiority did not make him popular”
“after that failure he lost his confidence”
“she spoke with authority”
Definitions, synonyms and semantic relations for self-assurance come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.