verb (used without object), RSVPed or RSVP'd, RSVPing or RSVP'ing.
to reply to an invitation: Don't forget to RSVP before Thursday.
noun, plural RSVP's.
a reply to an invitation: He sent a lovely bouquet of flowers with his RSVP.
(used on an invitation to indicate that the favor of a reply is requested).
1895–1900; < French r(épondez) s('il) v(ous) p(laît) please reply