Someone who is obsessed with brands on clothing, ranging from top designer brands to unknown designers. They will look at a tag and go, "Oh..of course you should like it..it's a shirt from LMBD!".
Most of the times, they don't even know that whatever's on the tag isn't a top designer, and assume that every tag inside a clothing that says a company is a major designer. They go twice as crazy if they see the tag lists an actual top known designer company like Juicy Couture or Ralph Lauren or something and go triple crazy if it's on sale. An example of a brand geek is my mom, probably what several moms are.
Mom: Hey this top is nice..
Me: Uh..it's all ruffled with pink flowers and it looks like something only grandma would wear.
Mom: Look! It's from BRTC Fashyuns!
Me: Who are they?
Mom: Big designers of course.
Mom: Hey look..a nice jacket!
Me: Mom, it's pale pink. Doesn't really go with my tone and not one of my favorite colors..plus it's like three sizes larger, and it has these weird polka dots and little cat buttons.
Mom: I know! So pretty huh! Especially the little cat buttons..Ooh look it's from OSA"
Mom: A really good company..
Me: *in head: mom you're a brand geek. no offence.*