A gesture of approval between two guys that believe the other is worthy of bro-hood. Usually between two people who have never met, but can also be used with someone who you don't have time to talk to.
"This guy at the airport gave me a bro nod as he passed by me, you could tell he was a true bro"
Bon Chez is a dickweed because if he bought a G4MX420 and is bitching beuase his stupid ass didnt read around abit to learn the the MX series was shit.