Liquefaction (液状化 Ekijōka) is the ability to liquefy through metal and other solid objects.
Super Buu uses the technique as part of his Dangerous Liquid Bomb.
The Sigma Force and General Rilldo use it in their battles against Goku, Pan, and Trunks. Natt uses this ability greatly when messing around with Pan, liquefying through another part of a wall when she was about to attack. The other Sigma Force members use the ability during their battle against Goku.