Definition
to not honor a promise, or to alter a decision or agreement
顛謝；顛背制定
He promised to support the project forever, but later went back on his word.
他承諾會永遠支持這個項目，但後來卻食言了。
If you decide to back out halfway, it will make you lose your friends' trust.
如果你決定半途而廢，這將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，因為她知道她無法背離與客戶的協議。