I know absolutely nothing about skateboarding but what I do know is how to google things ;) Here is only one article about skateboarding slang and there are tons of them out there: http://skateboard.about.com/od/skateboardingdictionary/a/Skateboard_Slang.htm

Sk8r

разумно предположить, что само слово "скейтер" это прямая калька с английского skater