na-adjective, noun
thoughtlessness; indiscretion; lack of judgment
Describes acting without careful thought or good sense; often used for rash or imprudent behavior.
彼の無分別な発言が問題を大きくした。
His thoughtless remark made the problem worse.
若いころは無分別な行動が多かった。
When I was young, I often acted without thinking.
無謀 implies reckless daring without regard for danger, whereas 無分別 is broader and can refer to any imprudent or unthinking act.
Compound of 無 (mu, 'without') and 分別 (funbetsu, 'discernment, judgment'). The word follows a common Sino-Japanese pattern for negation.