A state of being, replete with personality tendencies so incredibly vile and off-putting that there is simply no other term for their level of social communication. A complete lack of anything even remotely resembling a clinical attitude (even a negative one).
"Bro, gimme a drink."
"I SAID gimme a DRINK. It's fuckin' HOT."
"Dude, you need to check your asstitude at the door."
An asstitude is used to describe someone who has the attitude of an asshole.
Heather has such an asstitude.