The commonly used parental threat (usually empty threat) of intimidating one's child (or other subordinate) into doing what is asked of them. Very often used on defiant children when they refuse to go to bed or obey their parental figure.
Son: I'm not going to go to bed...I'll stay up as long as I want!
Dad: The hell you are! Get to bed or else I'm coming in there with a stick!
(noun): Used as an additional way to agree to a statement after someone has already stated "me neither"; used as an additional "me neither" when you are the third person to agree.
Mallory: I always enjoyed Paul McCartney's style, but I'm not crazy about the new look.
Daniel: Oh, me neither..
Emerald: Me threeither.