The term "boshee" is slang for bullshit, often used in terms of something that is cool, much like "Thats the shit dude!", but is also used for bad situations or circumstances, much like "Thats shit man. Total bullshit."
Reggie Bush was one of those "phenomenal" running backs. Even though he hasn't produced alot in the pros, everyone still remebers his speed and ability to get passed defenders when he played for USC.