The atbrosphere is a special layer of the (larger) atmosphere, created by (and occupied by) the bro.
Only accessible via high and mighty ego and/or the lifted truck or jeep characteristic of the bro himself.
There is also a special layer of the atbrosphere only accessible via low riding sportscar or kegstand.
Contains roughly 40% douchebaggery (see: douchebaggery), 20% racism, 20% shitty music, 10% homophobia, 5% homoerotica, 3% ignorance (an isotope of douchebaggery), 2% oxygen, and 20% dumb, because bros can't do arithmetic.
Bro A: "Bro, there's too many bros at this party. Like, this atbrosphere is enbroaching on my brovado."
Bro B: "Bro, don't make me beat your ass for using so many big words."
Bro A: "Sorry, bro, I got a little broverwhelmed for a second there."
Bro B: "..."
Bro A: "Uhh...I mean...JAGER BOMBS! NO MORE QUEERS! FUCK YEAH!"