To skive is British slang for the practice of avoiding responsibilities because you want to do something more fun or just don't want to do what you should be doing. In the context of schooling, this is known as truancy. In the military, this is known as desertion. (Thanks Wikipedia!)
So Amy hit the nail on the head - way to go! Jan, well I don't know what to say about your definition. I think you are thinking about some past life experience or something. Kristy's guess was close, only because she has probably done her fair share of skiving at the sleepovers she mentioned.
So if you get a chance this week, make sure and save some time to do a little skiving - relax, put off that load of laundry. Allow yourself that all important downtime to bunk off for awhile. If the British put their stamp of approval on such activity, well that's good enough for me!