Comes from german meaning "love for cock". It has changed over the years and is now a slang for a sex position in which the male lies on his back ad the woman on top of him saluting Hitler. If one is called a Spousta, it can also mean that one has an unreal rack. It is meant as a compliment and one should immediately go bang whoever said it.
Look at her doing the Spousta on him.
Damn girl, you are a Spousta and have an nice ass