A dude and/or bro who loves hanging out with other dudes and/or bros and getting that warm feeling of brotherly, platonic bro-love. To that end, yeahbros are usually followers, and often tell bad jokes. They are annoying and heterosexual to a fault.
Origin of the name: "Yeah, bro! Totally, bro!!"
Steve wishes he had a crew of yeahbros just like the guys on Entourage. What a toolbox.