Being exclusionary means deliberately leaving out certain people or groups, like an exclusionary club that won't admit anyone who's shorter than six feet tall or who has red hair.
When something is exclusionary, it's limited to specific people or only those who belong to certain groups. This adjective has a negative connotation, because excluding people, especially for reasons out of their control, is usually unfair. Exclusionary comes from the Latin exclusionem, "a shutting out" and its root, which means "to shut." An exclusionary game of beach volleyball shuts out certain people, while making the game inclusive allows anyone who's interested to join in.