0 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.
1 to answer an invitation saying whether or not you will attend: --
I got a party invitation in the post, and I called to RSVP.
2 abbreviation for répondez s’il vous plaît (= French for "please answer"): --
RSVP by October 9th.
3 used at the end of a written invitation to mean 'please reply': --
RSVP by October 9th.