To become acutely anxious, restless, irritable, irrational, and/or depressed from remaining for too long in an unstimulating, confined, and/or isolated environment. "Stir" in this usage is a slang word for prison. We thought taking our family vacation in a tiny cottage out in the country would be a nice break from city life, but we all went a bit stir-crazy after a few days. The doctor said I need to remain in bed as much as possible, but I'll go stir-crazy if I can't get out of the house at least once a day!