It is a place where you do not have a field of vision. Often if your side mirror on you car and the rear view are not properly aligned you can have a blind spot. There is also an art photography magazine that goes by the name Blind Spot. There is also a medical blind spot. In ones vision you can have a place absent of vision.
A blind spot in a vehicle is an area around the vehicle that cannot be directly observed by the driver while at the controls, under existing circumstances. here is a site with more info http://en.wikipedia.org/wiki/Blind_spot_(vehicle) hope this is what you were referring to