That’s her/his/their/your problem Definition 1 of 2Pro Tip 1/3Personal Responsibility Suggests the person must deal with their own issues, without expecting help. If he lost his keys, that's his problem. Pro Tip 2/3Blunt Dismissal Indicates a blunt or unsympathetic dismissal of another's concerns. She missed the deadline? Well, that's her problem. Pro Tip 3/3Conversational Cue Signals the speaker's unwillingness to discuss the matter further. You don't like my decision? That's your problem, not mine.