Wiktionary
guest speaker
n. Person who has been invited to present a speech at an event where they are not the host.
Usage examples of "guest speaker".
You'll be the guest speaker on Bertram Scudder's program, tonight, at ten-thirty.
The guest speaker came briskly forward, and grinned expansively at the crowd, seeming to swell under their approval.
He took that podium as merely a guest speaker, president of a smallish country in the eastern European bloc.
Dieter Pan, wearing a dark green jumpsuit and wrapped in a warm cape, as if he were cold, sat isolated in the guest speaker's chair, looking cranky and nonplussed.