go back on 背信；背弃；出卖；违约；背叛
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go back on one‘s word
食言
He never goes back on his word。
back-on他从不食言。
He would rather die than go back on his friends。
back-on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。
