Using both sides of a wad of toilet paper to wipe your ass after taking a shit in order to conserve. Originally considered as a way to save money for frequent shitters by buying less TP but used more often by broke college students or military personnel in the field with limited access to said TP.
Wes: There's only one roll of TP left in the bathroom till payday. Piiiissssss!!!
Nick: Looks like we're gonna have to budget wipe till then man. Shiiiiiiit!!!