- Marked by a lack of responsibility: irresponsible accusations. (adjective)
- Lacking a sense of responsibility; unreliable or untrustworthy. (adjective)
- Law Not mentally or financially fit to assume responsibility. (adjective)
- Not liable to be called to account by a higher authority. (adjective)
- One who has no sense of responsibility. (noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.