A word commonly used by french people when expressing extreme excitement or happiness; commonly used in rejoinders.
Rejoinder guy: jai recu un 18 sur mon examen... YOUPI!
Brigitte: Quoi the fuck?"
The Swiss-French method of writing the word "Yippie". Is used in the same way, but is crudely misspelled; like most things French...
Marina: i went shopping youpi!
Alek: you bought that French kids yoghurt?