(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.
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi