to go back on one's word
他才答应, 马上就变卦。
He'd just agreed, but then straightaway changed his mind.
你这是变卦啦。
You're going back on your word.
汉译英翻译词典收录86165条汉英翻译词条，基本涵盖了全部常用中文字词的英语拼写、翻译、音标、读音、用法、例句等，是英语学习的有利工具。