It's what happens when it's raining really hard; you can actually wind up riding on a thin film of water, and your tires don't have any contact with the road. about all you can do is take your foot off the gas, and pray. St. Jude is most effective at this sort of situation, as well as St Dymphna (she's the patroness of the mentally ill, which you pretty much have to be in order to be driving in those conditions.)