v. phr. 1. To turn against; not be faithful or loyal to. Many of the man's friends went back on him when he was sent to prison. The boy's father told him not to go back on his promise.
Compare: BACK DOWN, TURN ONE'S BACK. 2. To fail to do necessary work; not work. Grandfather's eyes are going back on him.
Compare: BREAK DOWN 4 , GIVE OUT.