be out of (one's) brain(redirected from be out of their brain)
be out of (one's) brain
To be heavily intoxicated by drugs or alcohol, especially to the point of becoming unconscious, nonsensical, or out of control. Primarily heard in UK. I think someone might have spiked Jack's drink with some kind of drug, because he's out of his brain all of a sudden. Jane always gets really violent when she's out of her brain like that. I had to take my brother away from the party because he was out of his brain on LSD.