There are a lot of definitions for this word and pretty much most of them are right, but they're all leaving out a vital detail : Gaming isn't just playing one company's systems and only the systems of that one company. To be a true gamer, you accept that a good game is a good game and you shouldn't give a crap what system it's on.
Guy 1: I only play games for PS3.
Guy 2 : Not me I'm a true gamer. I play all good games. Xbox, Nintendo, Play Station, PC, whatever.