Wiktionary
frat boy
n. (context US English) A member of a fraternity in a college or university
Usage examples of "frat boy".
The smell of pizza mixed with the rich scent of wet garden, and Ivy came in looking like a frat boy’.
Lanny Wilcox wasn't going to attract gold diggers on a GS-II's salary, and though there was no accounting for taste, Anna couldn't see a balding man in his fifties with the housekeeping instincts of a frat boy as anybody's idea of a sex toy.