RSVP
uk/ˌɑː.res.viːˈpiː/us/ˌɑːr.es.viːˈpiː/abbreviation for "répondez s’il vous plaît", French for "please reply"; used at the end of a written invitation to mean that you should let the people who invited you know whether or not you are coming:
RSVP by 9 October.
RSVPverb [ I ]
uk/ˌɑː.res.viːˈpiː/us/ˌɑːr.es-/informalto answer an invitation saying whether or not you will attend:
I got a party invitation in the post, and I called to RSVP.