Addressing the GM or other players, as players, to discuss aspects of the plot, character development etc. Usually done out of character.
Metagaming means using out-of-play information to aid your in-play character. Anything heard while out-of-play IS NOT known to your character unless told to him in-play later.
Metagaming is a part of the game that adds replay value but does not effect the object of the game. An example of metagaming is a chat system that is incorporated into the game. See the game is Yahoo Chess. If you make friends on Yahoo Chess, you'll want to return to see them again.
Metagaming is a broad term usually used to define any strategy, action or method used in a game which transcends a prescribed ruleset, uses external factors to affect the game, or goes beyond the supposed limits or environment set by the game.
In role-playing games, metagaming is the use of out-of-character knowledge in an in-character situation. A character played by a metagamer does not act in a way that reflects the character's in-game experiences and back-story.