a zip ghost is a ghost that is fast, mostly because it is 300+ years old. ghosts can travel faster the older they get, and usually after turning 300 they are considered zippy and are recognized by the ghost community by having a ceremony celebrating their zippyness. zip ghosts are also alot scarier than younger ghosts, because they are obviously faster and are better at just being ghosts in general. plus most old people are creeps anyway.
james- what was that!?
thorn- it moved really fast and was hard to see, it was probably just a zip ghost.