what does "flip the bird" mean?

I mean in this sentence "A buzzer sounds sharply in the distance. without looking up, he lifts his middle finger up on one hand and flips 'the bird' , holds it a moment.drops it." I dont know what he is doing.

Solution 1:

He is sticking his middle finger up. It is an obscene gesture basically implying that one should initiate sexual relations with oneself.

In this context, he is telling the buzzer to "f--- off," expressing complete contempt for what it represents.

(I'd paste in the graphic, but it wouldn't be terribly nice to my fellow Americans reading the page. That said, if you drive the Beltway here in DC, it won't be anything new. )

Solution 2:

I'm not an American, but I'm pretty sure it means sticking one's middle finger up, which is rather rude.