irresponsibility; irresponsible
Used both as a noun and as a な-adjective to describe a person, action, or attitude that lacks a sense of responsibility or accountability.
His irresponsible attitude really makes me angry.
そんな無責任な発言は許されない。
Such an irresponsible remark is unacceptable.
His irresponsible remark caused a problem.
He irresponsibly abandoned his job.
I was appalled by his irresponsibility.