Warmie refers to people who aren't seen as very cool or try too hard to fit in around those that are defined as 'cool'. Warmie's take on fad's way too late and instantly use new words they hear, or buy knock offs of the newest fashion (fake supreme hats for instance) to fit in with others around them.
Laura:u seem pretty cool what's your secret?
Kane: what do u mean? none i just do what i feel is right...
Laura: yeh but those trainers are in fashion atm
Kane: sorry, wouldn't kno warmie