If an action or event is impossible, it cannot happen or be achieved.

It was impossible to sleep because of the noise. 噪音太大，无法入睡。

It seems impossible that I could have walked by without noticing her. 我似乎不太可能走过而没有注意到她。

He made it impossible for me to say no. 他使我无法说不。

She ate three plates of spaghetti and a dessert? That's impossible. I don't believe it! 她吃了三盘意大利面条和一份甜点？那不可能。我不信！

An impossible situation is extremely difficult to deal with or solve.

It's an impossible situation - she's got to leave him but she can't bear losing her children. 这是个极其艰难的处境——她必须离开他，但却舍不得孩子们。

An impossible person behaves very badly or is extremely difficult to deal with.

I had to leave the job because my boss was impossible. 我得辞职，因为我的老板实在是太差劲了。

My niece is impossible when she's tired - you can't do anything to please her. 我侄女累的时候很难相处——你做什么也无法使她高兴。

something that cannot be expected to happen or exist

She wants a man who is attractive and funny as well, which is asking the impossible in my opinion. 她想找一个有魅力又风趣的男人，这在我看来是不可能的事。