Stands for Insanely Awesome Bitch, something that describes the great gynecocynic cynophile M and her utter epitomeness of pulchritude and bitchitude; can be extended to any girl who can be both awesome and a bitch at the same time, thus making them insanely entertaining.
It's what all of M's friends call her, and was first invented and used by the effulgent Zorbalicious.