Metagaming=>
It is a little confusing as used here compared to as used elsewhere.
Cross Gaming: is considered illegal/cheating (except in specific team tournaments where this is allowed) is where you say you help me in game X and I will help you in game Y
Metagaming: In many face to face tournaments and as I believed used in Australia initially for their multi-tournament ranking called Bismarck Cup, or Grand Prix elsewhere, is when you make a decision in a specific game based not on the situation in that game but how it affects you over all in the greater ranking in the tournament or the larger ranking contest. A classic example of this which was quite a scandal when it happened was when a player in the final round of a tournament threw a game to another player when he realized that the impact of it would be to depress the score of another player in that game that was in contention to win that tournament while also killing the prospects for another player in contention for winning the Bismarck Cup so that the schemer could then win that Cup as he had no chance in the tournament in question.
Metagame as used here seems to be more of a situation of Cross Boarding as described above.
Metagaming in terms of 'outside influences' on the game in question is really very vague here. For example numerous players I have encountered have taken all sorts of postures in games I have played here that have nothing to do with the game being played but are based on the point system/ranking system that is played within this site. Is that metagaming with outside influences?
Is attacking someone because of their Forum Comments an issue of metagaming as I have seen here. Probably in my book it is poor sportsmanship and not true meta gaming as the 'meta' aspect does not relate to gaming at all. In the same view of mine, which is again biased by FtF, Postal Play and Play outside of this site, I would not call attacking someone because of their political, religious, ethnic views or reality or because you thought they were an internet stalker, as a metagame aspect, but again simply as poor sportsmanship.
As another extreme if you go down the street of it being metagaming to attack people for some outside influence, you might say that attacking someone for something that they cannot change would also qualify as meta-gaming in the negative sense, then within that definition attacking someone who is seen as a better player than you would also qualify as a metagame negative act, after all you cannot change what you had for breakfast, let alone the history of your skills.
So it is tricky situation at times.