A bitchmistress is an obstreperous and obnoxcious cunt of a woman who has a willing yet sniveling husband, trick, or boyfriend in tow. She makes him do everything for her and complaines the whole time, spending his cash and bitching. Meanwhile he eagerly grovels at her feet.
Adj: An act that would commonly be performed by a bitch (definition #4). Used to describe the act itself. May be used regarless of gender of implied person.
"Dude, she slashed your tires? That's bitchenistic!"