The word "unhinged" describes a state where someone appears to be mentally unstable, irrational, or out of control. It can refer to someone acting in a strange or erratic manner, as if they have lost their grip on reality or their normal emotional responses.
The word "unhinged" comes from the prefix "un-" meaning "not" or "opposite of," combined with "hinge," which refers to the movable joint of a door or gate. In a metaphorical sense, to be 'unhinged' implies that one has lost the 'hinges' that keep their thoughts or emotions in place.