Definition
to not honor a promise, or to alter a decision or agreement
食言；食背制定
He promised to support the project forever, but later went back on his word.
他承诺会永远支持这个项目，但后来却食言了。
If you decide to back out halfway, it will make you lose your friends' trust.
如果你决定半途而废，这将使你失去朋友的信任。
She felt uneasy because she knew she could not go back on her agreement with her client.
她感到不安，因为她知道她无法背离与客户的协议。