Hardcore.
You can read very different meanings of the word "hardcore" gamer.
Places discussing videogames related to the letter "V" would like you to believe that a hardcore gamer is one who doesn't follow the crowd. One who is special, unique, someone who stands out and is totally fucking awesome. Thats nice and all, because who woudn't like to be unique? Thus the term is used to describe people who play older, less popular, harder to colplete games. The average gamer woudn't get why they play the same game all over again because they are considerd "casual", they follow the pack, they buy whatever game gets enough publication, is praised by game reviewers, ...
Both groups play different games but for mostly the same reason; to have fun.
But seeing the group of gamers who play games a few hours a week is much bigger then the group who plays several hours a day, a certain gap between groups has started to exist.
Those who have been playing for a long time (in years/decades), (probably the group who plays a few hours a day) see alot of games using recycled ideas, stuff dropped out of games, stuff they enjoyed, stuff the developers now expect us to play for ontop of the price you've paid for the game.
This group obviously doesn't like the fact games get more expensive, shorter, and more-so they dont like the fact that that other group doesn't seem to care.
Thus they use the term Hardcore gamers to describe themselves as a group who don't follow the pack, who are "the true gamers", something every gamer should try to become as it is the only way to enjoy games.
They add a positive meaning to the word hardcore, a mindset that says the true hardcore gamer is better then the casual, because he is "different".
But to me however;
Beeing a hardcore gamer is having a certain mindset.
You enjoy playing videogames, obviously, but you do so because of more reasons then just having fun.
You have fun - because you win.
And because of that you will do what it takes to win. You will play longer, more dedicated, pay more attention to certain aspects (learn the shortest routes, learn what weapons are better to use on what ocasions, learn to think how the enemy would think, ...).
You play to win. This can be in any sort of game, think min-maxing in RPG's, think buildorders in RTS, think watching replays of FPS matches.
Those players will often be discussing in fora, learning new tactics, comparing strategy's, theorycrafting.
But they do this - because it allows them to get the advantage - to win.
They dont get mad when they lose a game, instead they think, what went wrong?, how can i prevent this?
They basicly go the extra mile to ensure they get what they desire - the win.
Thus they will also be found in the more competitive scene of gaming.
But just winning isn't enough.
The winning is a result of an underlying idea, the idea of beeing better then your opponent, beeing able to outmanouver him, to outsmart him.
you can play a game on easy and you will win.
But the hardcore will for instance play on the hardest settings and still (try to) defeat the game.
Hence the competitive scene is the ideal place to fight against people with the same mindset, people who also want to win at all costs, who also went the extra mile, who counter your mindgames with mindgames of their own.
All in all hardcore gamers, just as any other kind of gamers, plays games, but with a different mindset.
This is my view on the 'hardcore' gamer.
I could be wrong.
*edit*
Wops, went a dit overboard on this one it seems

inb4 wall of text