I think "hybrid" is correctly applied as a very broad term. Anything not purely a road bike, or purely a mountain bike, that falls somewhere in between, I will call a hybrid. Flat bar road bikes fall under this designation, so do the new dual sport/multi-use bikes. Frame geometry is the major differentiation that is less obvious. My Trek 7.2 FX apparently can be described as a "light touring" geometry, with longer chainstays and slightly more upright seating than a "flat bar road bike" would have.