Everyone has a different definition, and it doesn't mean much, but to me, a gamer is someone who may or may not specialize in a particular game/genre, but will try out and play various genres. But I think the key aspect of a gamer is his love and appreciation for video games. He not only appreciates them as a form of entertainment, but also as a peice of art, and acknowledges those that have put their blood, sweat, and tears into a game. A gamer will also try his best to keep up with the direction of where the game industry is going and tries to keep up with news and the like.