noun
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.
彼は不所存者で、周りの迷惑を考えない。
He is a thoughtless person who doesn't consider the trouble he causes others.
Compound of 不 (negative prefix), 所存 (one's thoughts or intentions), and 者 (person). Literally 'a person without proper thoughts/intentions'.