A name given to an idiot, asshole, bitch, slut, or just a random person. An insult to someone.
Emee, You're a fucking cunt hat.
The name given to the disposition of someone that is behaving like an arsehole, or cunt. Behaviour includes excessive swearing, name calling, selfishness, making others, including friends, feel like shit about themselves. Generally the person wearing the cunt hat is intoxicated or hungover.
Bec: "Jackie's really got her cunt hat on tonight"