Public fingerbanging. Usually carried out by an inebriated male in a location he misperceives to provide privacy requisite for the desired degree of intimacy (i.e. against a chain-link fence bounding an outdoor party). Traditional costume comprises leather shorts on the swartzing agent and, obviously, a skirt on the action's receiver. Not to be confused with a futon-fingerbang.
Swartzing was first defined in New Haven, CT, and has since spread in usage to much of the Northeast.