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.
"what the hell is Hunter doing to that chick?"
"Looks like he's giving her a good swartzing"
"Is he wearing leather shorts too?"
"He is, indeed, his technique is flawless"