have no back bone
性情懦弱
A：What do you think of Frank?
A:你认为弗兰克这人怎么样?
B:He's all right. But I think he seems to have no back bone.
B：他人挺好，就是好像性情有点懦弱。
A:Why do you say that?
A:你为什么那么说昵?
B:Whenever things get tough, he gives in.
B：每当事情变得棘手时，他就会屈服。