The French word "coucou," koo koo can be used as an exclamation meaning "hello" or "hi." It is similar to the English excalamation, "peek-a-boo!" It is also used to refer to the cuckoo clock.
- Coucou, Pierre, c'est moi !Hi, Pierre, it's me!
- Coucou, il y a quelqu'un ?Hello, is anyone there?