How to say "unheard-of" in Japanese

• 破天荒はてんこうCommon
  na-adjective, nounCovers unheard-of daring rather than plain novelty: it describes a person, or their behavior and achievements, as boldly defying all precedent, typically with an admiring tone.
• 前代未聞ぜんだいみもんCommon
  no-adjectiveThe literal 'never heard of in history' choice: it describes events, incidents or achievements with no historical precedent, typical in news reports of a shocking first or a record-breaking feat.
  犯人はんにんを弁護べんごしてた弁護士べんごしが実じつは真犯人しんはんにんだったなんて、前代未聞ぜんだいみもんだ。↗

  It's totally without precedent for the suspect's attorney to be the true culprit.

Use 前代未聞 for events, incidents or records with no precedent in history, and 破天荒 for bold, unconventional people or behavior whose daring defies precedent, usually with an admiring tone.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 破天荒はてんこうunheard-of
• 前代未聞ぜんだいみもんunheard-of
• 希代未聞きたいみもんunheard-of
• 未曾有みぞうunprecedented
• 史上空前しじょうくうぜんunprecedented in history
• 前人未発ぜんじんみはつunprecedented