thoughtless person; inconsiderate person
A somewhat formal or literary term for someone who acts without due consideration for others or the situation. Not an everyday insult; more likely to appear in written criticism or formal speech.
He is a thoughtless person who doesn't consider the trouble he causes others.
Similar meaning, but 無分別者 emphasizes lack of judgment or discretion, while 不所存者 focuses on lack of consideration or thoughtfulness.
軽率者 implies rashness or impulsiveness, whereas 不所存者 stresses thoughtlessness or inconsiderateness.
Compound of 不 (negative prefix), 所存 (one's thoughts or intentions), and 者 (person). Literally 'a person without proper thoughts/intentions'.