[go back on] {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.