不謹慎|ふきんしんfukinshin[2]nakadaka (mid-high)

1. na-adjective, nounimprudent; indiscreet; immodest; indecent; inconsiderate; inappropriate

• Synonym軽率けいそつNeutralActing without thinking it through; common in both speech and writing. 「不謹慎」 instead targets remarks or behavior that lack decorum or tact.
• Synonym軽はずみかるはずみNeutralColloquial word for acting rashly on a sudden impulse. 「不謹慎」 is about words or behavior that are indecorous, not about impulsiveness per se.
• Synonym軽々しいかるがるしいNeutralDescribes remarks made too readily, without due weight; carries less of the sense-of-occasion coloring that 「不謹慎」 has.
• Related不心得ふこころえWrittenWritten word for an improper attitude or conduct; covers both habitual misbehavior and a single lapse, as in 「不心得な発言」.
• Related軽忽きょうこつWrittenRare written word for rash, thoughtless behavior; can also mean laughable or disdainful. Unlike 「不謹慎」, it is not about disrespecting a solemn occasion.
• Related無分別むふんべつWrittenRare written word for acting without judgment or sense of right and wrong; whether the occasion is solemn is irrelevant.
• Related不所存ふしょぞんWrittenRare written word for doing something wrong because one failed to think it through; the fault lies in insufficient thought.
• Related無思慮むしりょWrittenRare written word for thoughtlessness, failing to think things through; close in sense to 「無分別」.
• Related弁えのないWrittenWritten phrase for lacking a sense of propriety, not knowing what weight a situation carries or how to read the occasion.
• Related弁えの無いWrittenKanji spelling of 「弁えのない」 with the same meaning and written register.
• Antonym謹慎きんしんWrittenWritten antonym: discreet self-restraint; also a disciplinary confinement or suspension served for reflection.
• Antonym真面目まじめNeutralSerious and earnest; the opposite of joking around at a solemn occasion, which is what 「不謹慎」 suggests.
• Antonym慎み深いつつしみぶかいWrittenWritten word for discreet, humble restraint; the opposite of 「不謹慎」's failure to hold back.

Use 「不謹慎」 for words or behavior that are frivolous or disrespectful of a solemn occasion, as in 「不謹慎な発言」. For plain rashness pick 「軽率」, for impulsive acts 「軽はずみ」, for remarks made too readily 「軽々しい」. 軽忽, 無分別, 不所存, 無思慮, 不心得 and 弁えのない are rare written alternatives; 謹慎, 真面目 and 慎み深い are the opposites.

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

1. 慎つつしむことがないこと。不真面目ふまじめであること。