I view "casual gaming" as a group of friends who will occasionally do some roleplaying. No set schedule, no long-term campaigns, no long-standing commitment to a rule-set, and random newbies might show up to any old session and just play a fill-in character. I don't see it as having anything to do with your dress code, the location where you game, or the amount of alcohol you're imbibing during the game.
Having said that, I'm not a casual gamer. Our group of regulars meets every Thursday night (or every other Sunday, depending on the players), regular as clockwork. Once people have arrived, we get down to the serious business of gaming. People who aren't there to play the game or act distracted are not welcome in the group... and everybody knows that up front, and welcomes it. We play long-term campaigns, get attached to our characters, and we commit to our rule-sets for the approximate length of a modern marriage (8 years).
Now, that doesn't stop us from socializing outside the gaming sessions. We'll have lunch together, and talk about our personal lives and ambitions, and go out to a club, and do a movie night. It also doesn't mean we're a bunch of munchkins; most of us just play the kind of PC we want to play. But everyone is committed to the concept that you'll make every effort to be there for the weekly session and, for the 5 hour period when the dice are being chucked, the Game is the Thing.
In general terms, each of the seven regular members of our group will miss less than 6 sessions per year (i.e. 90%+ attendance from every player). Most of us are married. And, fortunately, most of the married ones have very understanding partners....
