an abbreviation for cross-generational, can describe both a relationship or a genre of gay porn.
1. My husband is 44 and I'm 24, so our relationship is x-gen.
2. Dads Fucking Lads just released their latest x-gen porno.
'a close friend who tries to date your ex-girlfriend right after you've broken up'
Susan dates Bob. Bob is friends with Paul. Susan and Bob stop dating. Susan starts dating Paul. Susan, Bob and Paul all work together.
A fake vitamin used to explain an overly large dick.
"Damn man, he has to be takin some vitamin X"