In furtherance of this choice, it so happened that a ship lay in the harbour; one of those unquestionable cruisers, frequent at that day, which, without being absolutely outlaws of the deep, yet roamed over its surface with a remarkable irresponsibility of character.
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.