1.
irresponsible, lacking a sense of responsibility
Failing to take responsibility for one's actions, duties, or statements. Used to criticize people who do not follow through on obligations or who make careless remarks without considering the consequences.
Common patterns
Functions as a な-adjective: 無責任な態度 (an irresponsible attitude). Also used as a noun: 無責任を問う (to question someone's irresponsibility).
Usage
A strong criticism word. Combines 無 (without) and 責任 (responsibility). Used in everyday conversation, workplace settings, and political commentary. The opposite is 責任感がある (having a sense of responsibility).