00

00 is a term that is short for the OPIUM label made by Playboi Carti.
Mostly seen in usernames like "00Calvin", and in fan Instagram accounts, "00pium_00pium:

Person 1: You still listen to Carti right?
Person 2: Yeah what about it?
Person 1: Are you 00?
Person 2: What the fuck does that mean?
Person 1: Are you a Carti fan or not dickhead?