Ghostdoggin' is when someone creeps into your house at night and slips under the sheets and nails your wife/gf. This was a very consensual bootycall agreement between both parties. Afterwards, the Ghostdog slips out into the night never to seen again until your girl hits him up.
Dude, when I brought that chick from the bar back to the hotel she totally asked to ghostdock with me. I told her I'll fart my own farts, thank you, and kicked her out.