Au revoir is the French way of saying goodbye. If you want to show off your knowledge of other languages, say "au revoir!" the next time you leave a room.
In French, this farewell literally means "to the seeing again," and in English it's also used as a goodbye. There are many words in the international family of farewells, such as adieu (also French), adios (Spanish), arrivederci (Italian), sayonara (Japanese), and auf wiedersehen (German). In English, we say bye, bye-bye, cheerio, good day, goodbye, so long, and "see you later."