The state of being completely inebriated. The term 'castled' is a combination of the German word schloss which means castle and the term sloshed which means very drunk. Additionally, the term 'castled' is based loosely around the term housed for getting very drunk. When one gets castled they are a step up from getting housed as castles are larger than houses, implying that getting castled is drunker than getting housed.
Ace: Dude, what happenned last night? Did you tag that fugly chick??
Gary: I don't think so, no one was in my bed when I woke up but i can't be sure; I was totally castled last night.
Ace: Gary look at Jimmy, he is so castled right now he can't even keep his head up.