A: Nancy is going out with David.
B: I hope not. David is a liar to the backbone.
A: How come?
B: He never tells anything true.
to the backbone
To the backbone的意思是“彻底地，纯粹地”。
E.g. He is an Englishman to the backbone.
E.g. I like it to the backbone.
E.g. He is honest to the backbone.
go out with：和某人约会
E.g. Do you want to go out with Mary?
E.g. I often go out with Cynthia but it's purely Platonic love between us.
E.g. It was exciting to go out with him for he was so handsome.