Someone who uses internet
meme in everyday life around normal people. This can be drawing
memes and letting them be seen publicly, using them when talking on
Facebook, Twitter etc., saying them in normal conversation.
They often think they're funnier when people are unaware of what they're talking about. Memefags are most commonly socially awkward people or early teens kids.
Though not everyone who knows memes, use them like this. People who are familiar with
meme but only use them in places where it's acceptable, when seeing someone using memes in a normal real life place, can often start raging.