Bail的意思是“保释、担保”，bail on someone是什么意思呢？请看对话：

    A: I waited two hours for you at the cafe. Why did you bail on me?

    B: There was an emergency in the lab and I had to stay there until midnight.

    A: Then, why didn’t you let me know?

    B: My phone was out of juice.

    A: Come on, you’re bailing on me for good, aren’t you?

    Note: We know that to “bail out” is to “rescue,” but why is this idiom so different in meaning? In fact, it is short for “bail out on,” which means to “leave someone behind,” like bailing out of an airplane with a parachute or out of a sinking ship with a lifeboat. The idiom either means to “desert the person when the going gets rough,” or simply “fail to meet up with someone,” which is obviously an exaggeration.