So what's a dude bro you ask?
Sunday, April 12, 2009 at 12:21PM Well here's a picture of an actual dude bro checking his physique before engaging in what I would assume would be a rowdy night of idiocy, bud light, shitty music, and trailer trash girls.

Jackass.
Here is the urban dictionary definition of said "dude bro" slightly modified:
White suburban male, usually 16-25 years of age, (although some never mature into true adulthood) hailing mostly from Orange County, CA and surrounding areas. Truth be told though, these social retards can be found all over the contiguous United States. Characterized by their love for rolling around in lifted (extreme) trucks with "Metal Mulisha" stickers on the back window and their over use of bandanas, black socks with shorts, spikey hair, belts with queer designs and belt buckles, SPY sunglasses, Volcom clothing, and trucker hats. Favorite bands include Kottonmouth Kings and Kingspade. The most annoying members of the dude bro family are from the 951 and 909 area codes of the Inland Empire of Southern California as well as the 661 Santa Clarita Valley and the 805 Antelope Valley... but more toned down (and slightly more queer) versions can be found in Orange County (714). Favorite drinks include Budweiser and Bud Light and when wanting to get really tanked, 211. Some of you know it as Steel Reserve. Catch phrases include: "DUUUUDE!!" and "Bra" (Bro) and the obvious "Dude Bro!" Dude Bro's seldom roam alone and can usually be found in packs of 5-10 people. Favorite sports include riding dirtbikes and monster truck rallys. Dude bros display a complete lack of originality and can quickly get on one's nerves. On rare occassion they will attempt to get into physical altercations usually throwing a punch that was meant to hit no one while simultaneously having their friends "hold them back."
In summation, they live a meaningless existence and try to infect those around them with their own massive amounts of stupidity. If possible, avoid at all costs and for the love of God do NOT procreate with them. Your child will grow up licking screen doors and baseball bats.
To the best of site owner's knowledge this image is not under international copyright.