To act excitedly and without careful thinking.
John has gone off the deep end about owning a motorcycle.
Just because you had a serious argument with your supervisor, you didn’t have to go off the deep end and resign, did you?
Mike warned his roommate not to go off the deep end and get married.
Some girls go overboard for handsome movie and television actors.
When Dan’s wife demanded a divorce, he went off the deep end again. This time he was shouting so that the whole neighborhood could hear.