軽はずみ|かるはずみkaruhazumi[3]nakadaka (mid-high)

1. na-adjective, nounthoughtless; rash; hasty; imprudent
   君きみが彼かれの申し出もうしでを受うけるとは軽かるはずみだったね。↗

   It was foolish of you to accept his offer.

• Synonym軽率けいそつNeutralSino-Japanese and slightly more formal; nearly synonymous with 「軽はずみ」, as in 「軽率な発言」.
• Synonym軽々しいかるがるしいNeutralFor speaking or acting too readily or rashly; often in the negative, as 「軽々しく言うな」.
• Synonym不心得ふこころえWrittenWritten/formal. Points to improper conduct or flawed character—a moral failing, not mere hastiness.
• Synonym浅はかあさはかNeutralFor shallow, short-sighted thinking; emphasizes lack of insight more strongly than 「軽はずみ」.
• Synonym無謀むぼうNeutralReckless disregard of consequences; far stronger than 「軽はずみ」.
• SynonymそそっかしいNeutralFor a scatterbrained, careless nature that leads to frequent mistakes.
• Synonym不謹慎ふきんしんNeutralFor remarks or behavior that are flippant or out of place, often an ill-timed joke.
• Synonym無分別むふんべつWrittenA written/formal term for failing to grasp what matters; a stronger condemnation than 「軽はずみ」.
• Synonym軽忽きょうこつWrittenWritten/formal and old-fashioned; means rash, and can also suggest something absurd or laughable.
• Synonym無考えむかんがえCasualColloquial and not very common; describes acting without thinking.
• Synonym卒爾そつじWrittenWritten/formal and old-fashioned; means abrupt or sudden, now mostly in 「卒爾ながら」.
• Synonym無思慮むしりょWrittenWritten/formal and very rare; in everyday speech say 「軽率」 instead.
• Synonym向こう見ずむこうみずNeutralCharging ahead without regard for consequences; stresses daring or foolhardiness.
• SynonymむやみやたらNeutralAn emphatic form of 「無闇」; stresses doing things indiscriminately or to excess, not a momentary lapse.
• Related不見識ふけんしきNeutralCriticizes another's words or deeds as showing poor judgment or bad form; 「軽はずみ」 targets a momentary lapse.
• Related軽薄けいはくNeutralFrivolous and shallow—a trait of character, whereas 「軽はずみ」 describes a momentary act.
• RelatedむやみNeutralActing or overdoing without good reason, as in 「むやみに信じる」.
• Related心無いこころないNeutralInconsiderate or coldhearted, and also unthinking; stresses hurting others' feelings.
• Related不所存ふしょぞんWrittenWritten/formal and old-fashioned; suggests misguided thinking or improper behavior.
• RelatedちゃらんぽらんCasualColloquial for slack, irresponsible behavior; the emphasis falls on a habitual attitude, whereas 「軽はずみ」 points to a single rash act.
• Antonym慎重しんちょうNeutralAntonym: careful and deliberate, weighing things before acting—the opposite of acting without thought.
• Antonym思慮深いしりょぶかいNeutralAntonym: thoughtful and sound in judgment, the opposite of acting on impulse.

For rash words or deeds in everyday use, pick 「軽はずみ」 or the slightly more formal 「軽率」. For recklessness that ignores consequences, use 「無謀」; for careless, scatterbrained behavior, 「そそっかしい」; for remarks out of place on the occasion, 「不謹慎」.

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

1. 軽妙けいみょうであること。
2. 軽率けいそつであること。