back out
phrasal verb with back verb uk/bæk/ us/bæk/
B2 食言
to decide not to do something that you had said you would do
You agreed to come. You can't back out now! 你答应要来的。你现在可不能说话不算数！
They backed out of the deal the day before they were due to sign the contract. 在原定签合同日期的前一天，他们决定退出这笔交易。