Of late, too, he looked somehow bloated and seemed more irresponsible, more uneven, had sunk into a sort of incoherence, used to begin one thing and go on with another, as though he were letting himself go altogether.
It was unreflecting of him, but it was just his irresponsible want of reflection that made him so confident that his father would give him the money, that he would get it, and so could always dispatch the money entrusted to him and repay the debt.
There are no more uses of "irresponsible" in the book.
Show samples from other sources
After much passing around of money Cousin Joshua was moved across the tracks and placed in state accommodations for the irresponsible, where he remained for the rest of his days.
Harper Lee -- Go Set a Watchman
"The fact of the matter is, we’ve been irresponsible," Marybeth continues.