Pronunciation (UK) IPA (key): /əˈsɜːt/ (US) IPA (key): /əˈsɝt/ Audio (US)(file) Hyphenation: as‧sert Verb Plain form assert Third-person singular asserts Past tense asserted Past participle asserted Present participle asserting (transitive & intransitive) When you asserts something, you say it with confidence. He asserted that he was innocent.Wikiwand - on Seamless Wikipedia browsing. On steroids.