To the curious person searching Google for this and being directed to my blog, the term refers to a region of one's shoulderblade. The ridgelike part that sticks out is the "spine" and supraspinous means "above the spine" or "above the ridge." "Fossa" means "low area" or "valley." Therefore the whole term means "Low area above the ridge."
Wouldn't it be cool if doctors and anatomicists would just speak English?
Hope that helps!
To those of you who have no idea what I'm talking about - that's OK. Obama is still a liar and the sun will rise tomorrow. That's all you need to know for now.