In role playing games, particularly those of the Japanese variety, the practice of gaining levels excessively in order to be able to defeat a boss character. The term is most appropriately used when the boss or bosses being levelled for can be normally defeated without too much challenge. In the case of wusselling up, the player in question lacks skill, or is a newbie.
Wusselling up should not be confused with bad game design that requires the player to level excessively as a matter of course. See Disgaea.
"lawls lawls, Billy had to wussel up just to defeat Jenova Life."