Word made up of two words, skate and hitch. It is basically hitching a ride while doing some form of skating. A person grabs onto the back bumper or fender of a vehicle and will be pulled along on an object. The most common objects people do this with are skateboards or a kind of roller skates/inline skates. This has been seen in various movies including Back To The Future and is also used in several video games including Tony Hawk's Pro Skater 4 and all other Tony Hawk games since 4, Jet Grind Radio and Skitchin' which was a game based in a large way on this particular activity. This is a way for somebody to reach a level of speed that would be near impossible to reach with just a skateboard or roller skates/inline skates alone. It is also very dangerous and can get you seriously injured if something goes wrong. Also the police frown upon this activity as well.
"Did you see Back To The Future where Marty skitched that truck in the beginning?"
"It is sweet you can now skitch in the Tony Hawk games."
"You'll need to skitch something if you want to get enough speed to clear that huge jump."
"That guy was trying to skitch a truck but it stopped suddenly and was pulled under and got ran over."
"That fool got busted by the cops for trying to skitch their car."