Typically found in Roleplay gaming. The act of taking one character from one complete game, and translating it into a completely different game, with little to no basis for doing so. Usually looked down upon as the sign of an underaverage roleplayer(Or one who does not want too subscribe to any lore or rules that the game already has set) by the community he or she interacts with.
Also considered a type of Metagaming.
A: (So.. your character is a viking.)
A: (Your flying a space ship, and you arent human. You do realize that this is a scifi game and humans are thousands and thousands of years away from being vikings.)
B: (Still a viking. Brought my character over from x game name here
A: (*sigh* Thats cross gaming, you know.)