The fratmosphere is the aura that permeates the fraternity/sorority house, party, and social event. Its use is not limited to just describing fraternity related functions and fraternity brothers are not uniquely talented in creating a fratmosphere.
An event where there is a fratmosphere is often characterized by men and
women dressing very much alike (possibly
popped collars on the men), the scent of the cheapest beers (
e.g. PBR or The Beast), "hunch punch", and
women posing in the "sorority squat" for photos.
"Dude, I went to this party last night with some of my
college buddies and we hit the two-story beer
bong just like old times... I'm not usually one to get that
wild anymore, but I got sucked into the fratmosphere of the party.