slang The ability to behave as a mature adult woman should. The phrase is typically used pejoratively to imply that one is not behaving in such a way. Come on, Linda, you need to put on your big-girl pants and own up to your lies. I know you're not a morning person, but put on your big-girl pants and go to work.
See also: pant
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.