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Phrase(s): *out of one’s mind [and] *out of one’s head; *out of one’s senses
Fig. to be silly and senseless; to be crazy and irrational. (*Typically: be ~; go ~.) • Why did you do that? You must be out of your mind! • Don’t drive so fast, Tom! You have to be out of your head!
McGrawhill's American Idioms And Phrasal Verbs