This four-character set phrase means 'to become intoxicated or carried away (by success, power, love, etc.) and lose one's good judgment.' It often appears with 被 in passive constructions (e.g., 被胜利冲昏头脑) or with 了 inserted between the two parts (冲昏了头脑) to indicate a completed state. Use it when someone loses their rational sense due to strong emotion or triumph.