phrase/ʒə vu.z‿ɑ̃ pʁi/
I beg you, I entreat you; please do, go ahead, be my guest; you're welcome (after being thanked)
“—Puis-je fermer la porte ? —Je vous en prie !” — "Can I close the door?", "Please do!"
Synonyms: de rien, je t'en prie
Literally, “I pray you (to do so)”.