1. Stains left in the seat undergarments. See also: "Skid Marks" and "Bacon Strip"
2. A contraction of "Script Kiddies". Script Kiddies are inexperienced young hackers that use programming scripts (Login, Visual Basic, et. al.) for malevolent ends.
1. Whoah! You scared the bejeezus out of me. Hold on. I gotta check my shorts for skiddies.
2. I can't believe a bunch of Skiddies got into my website and messed it up.
A act during intercourse, when you drag your ass across your partners chest, unaware you didn't wipe your assall the way leaving skid marks across her titties. Hence leaving skiddies.