go back on 背信；背弃；出卖；违约；背叛
go back on one's word食言
He never goes back on his word.
他从不食言。
He would rather die than go back on his friends.
他宁死也不出卖自己的朋友。
A:Something must be wrong with Bob recently.
最近Bob有点不太对劲。
B:Yeah,he's in a bad mood,coz some of his friends have gone back on him.
是的，他心情不好，因为他的一些朋友背叛了他。
