I think Meta-Gaming is like Porn. You can't quite define it but you can recognize it when you see it. That having been said, as a GM I expect and allow (therefore encourage) a limited amount of Meta-Gaming (As I define it). I Meta-Game myself to set up reasonable logical encounters that will be challenging to my players. If a player expresses things in game terms then that is usually okay with me. Sometimes it is the shortest most clear way to say something. But I also try to keep it under control. My players often ask for knowledge rolls to see if their character knows something the have guessed using slightly out of character info. I just chalk this up to most characters being more experienced/ living on the edge with killer instincts then most players are. I think it is mostly a matter of finding the group and GM's level of acceptance.
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