Referring to the size of a marijuana cigarette and/or cigar. Regarded in a sarcastic tone and used by those with 'college' student-like budgets (i.e. not a lot of money) to represent a marijuana cigarette and/or cigar fitting such a lifestyle.
A small marijuana cigarette and/or cigar
Come on over dude! I got a college fatty rolled up!
Yeah, I'm not high anymore, I smoked a college fatty with three other people...