When somebody has acted cuntishely on a frequent basis. Permacunt differs from cunt in that the reputation of said person has become so immensely cuntish that they will forever be deemed a cunt.
-"She is such a cunt, she will permanently be a cunt."
-"Yeah, man, she's a permacunt for sure."
To have permanently intoxicated yourself with alcohol and/or chemicals to such point where respectable levels of social and/or physical functioning become problematic; where you are also (quite possibly) chewing a lot.
In short, a state of complete and utter trashedness!
An aggressive and nasty girlfriend who won't allow her boyfriend to be himself, and will threaten all sorts of negative actions if said boyfriend wants to leave the relationship or pursue other interests.
That Sandra is a serious Permabint. She never gives the guy any space to be himself or to be on his own. Just awful.