Personally with the word "gamist" I mean mostly the attitude of reasoning in terms of codified rules, rather than in terms of what those rules originally represented.
So for example, for me a "gamist" thing to do is to unconsciously forget or consciously refusing to acknowlege what a certain PC's ability/action represents and instead just focusing on what the written rule allows or disallows explicitly, and what it doesn't explicitly forbid, and perhaps ignoring an eventual mismatch with the non-rules part of the description.
To give a more concrete example, let's say the rules include a special action that represents widely swinging your weapon to catch multiple targets at once, but then the rule forgets to explicitly mention "in a line" or "one after the other". A "gamist" attitude would be to ignore the fluff (i.e. the description of what the rules represent) and focus on the crunch (i.e. the description of the mechanics, how using the action works) and declare that it's possible to use this action to strike targets in any order (e.g. in directions NE, SW, NW, SE).
What's your take on the word "gamist"?
I think that's a precisely accurate definition.
Some uses would be:
-- Gamist highest value is "balance", as they worry if one build might somehow outstrip the value of another build, in DPS or some other measure. The engineers of the gaming world. They want an efficient and fair set of game mechanics.
-- Storytellers highest value is that "stuff makes sense". It's fine for high level Wizards to be scary powerful, and low level Wizards to be more easily killed than low level Fighters, because that just FEELS RIGHT -- the balance argument does not appeal to them. The liberal arts majors of the gaming world. For them, rules are not an end at all, but a means for a rough approximation of the kind of fantasy story they want to tell.
My example: In 3e context, a pure gamist trying to decide whether a new feat in the Net Book of Feats was a good add to their campaign would look primarily at the Balance rating.
A pure storyteller would look at whether what was described was an historical accurate combat manuever or had occured in a fantasy book/movie he had seen.
As a storytelling-oriented DM, I actually looked at both, but in an evaluation the "Shield and Spear" feat, the definitive reason I let it in was an illustration of that tactic being used, in a scholarly book about ancient Greek warfare. The fact that was historically REAL easily trumped any consideration of game balance for me.
I think a lot of bitter arguments here come down to "gamist-oriented" versus "storytelling-oriented" (which I think is to some degree the classic Sensing v. Intuitive divide in Myers Briggs personality types -- one of the hardest divides for people to understand each other on).
I see echoes of that divide in:
-- Combat-as-Sport (follow the rules and seek balance) versus Combat-as-War (creative solutions are fine, beating a scenario with a tricky idea is fine, monsters should be role-played to do what's sensible from the monsters POV not just as a brainless tool to "challenge" for the PC's and shouldn't fight to the death for no reason, etc., and scenarios where the PC's could get killed are fine too).
-- Balanced scenario building tailor to the PC's classes and levels versus old school "sandbox" setting design where "it is what is" and if you choose to take on the ancient dragon's lair at 1st level, or to challenge the tomb of the undead army without a cleric, you can, but you will die.
-- 4e feel (stat blocks for your powers, and a little bit of minor fluff in italics) versus old school feel (a lot of what the spell does in the text)