A way of saying wassup in a cool, un-loser-like fashion. Usually between friends and usually between boys/men. Can also be used between girls that are not extremely feminine or just want to be funny.
Defined by choices in clothing, hobbies, lifestyle, and women
A basic bro will gravitate toward such things as fantasy football, golf, untucked button downs (especially for evening look), own a significant amount of sports attire, Axe, man caves, women who wear large scarves and carry coach bags.