invitational
adj.adj. describing an event where only people who are specifically asked can join. It is often used for sports or meetings where you need an official invite to participate.
adj. restricted to participants who have been specifically invited. Often used to describe competitive events or academic seminars where entry is not open to the general public.
The school is hosting an invitational track meet.
Only the top ten players in the league were eligible to compete in the year-end invitational tournament.
The university hosted an invitational symposium, bringing together the world's leading experts in renewable energy to discuss policy shifts without the distractions of a larger, open-access conference.
Typically used attributively before a noun like 'tournament', 'meet', or 'conference'.