1.
wealthy/glamorous person; celebrity
A famous person, or more commonly in Japanese, someone who is wealthy, fashionable, and lives a luxurious lifestyle. The meaning has shifted from the English "celebrity" to emphasize wealth and glamour over fame.
Meaning shift
While derived from English "celebrity," セレブ in Japanese emphasizes wealth and luxury rather than just fame. A セレブ is someone who lives extravagantly — think designer clothes, expensive restaurants, and high-end neighborhoods. A famous comedian would not typically be called a セレブ unless they also project a wealthy image.
Usage
Often used as a quasi-adjective with な: セレブな生活 (a glamorous lifestyle), セレブな雰囲気 (a high-class atmosphere).