An annoying sub-culture of people who wear over sized clothes and flatbrim hats with stickers still attached. Also known as "yeah dudes" or "yeah brahs"
by antiflatbrim August 18, 2012
Someone that's into "extreme" sports such as down hill mtn. biking, BMX, motocross or anything that you can get "rad" with. A flat brimmer will wear a ball cap with a flat brim with Oakley sunglasses and can usually be seen drinking a Monster Energy drink. A flat brimmer will think he or she is better than the rest and loves to pose for photographs.
by Surlybob March 16, 2015