The entire phrase is borrowed from French. It means a thing that has already happened or been decided.

I had a bit of fun looking into this phrase - yes, it's a French word but it came into English via a travelogue on Spain(!) by an English writer. It's typical of English - especially British English - to borrow French phrases, and "fait accompli" is one of them. It's a "done deal", basically (ie. before you have any say in it).

Hahaha, Peachey, humorist :) I like this phrase, fait accompli, ladies and gentlemen! :) I didn't know that English often borrow french phrases.

Thank you for replies, friends. There is borrowed from French phrases in Russian, too. Most popular are "c'est la vie" and "Tête à Tête".