(1)Obviously a nickname for someone who is a female dog with no father.
(2)A word you shout in ones general direction when you've realized that they have no genitals, and then realized that you looked to see if they had genitals.
(3)One who is of bastardly bitchtastic proportions.
(1)Lassie is a classic example of a bitchastard.
(2)Dear God, where are your genitals Molly? Dear God... Bitchastard!
(3)Many students at RMSEL... (Dana, Austin, Kathy, you get the idea...)