Adjectival Noun/Adj./Intransive Verb.
Adjectival Noun: someone who acts childishly, immaturely, and bitchy, though he or she is a legal adult.
Adj: 1. Puerile; immature; childish though legally adult.
2. Bitchy, clearly overcompensating for lack of intelligence and security.
Int. Verb: To act in any of the above ways.
Adjectival Noun: "Why are you being such a saphy?"
Adj.: 1. "That was the most saphy thing you could have done, brat."
2. "I can't believe she did such a saphy thing. I hear Jane cried all night."
Int. Verb: "Yeah, bitch, don't saphy me."