What makes a CX frame?
 

Other than tires and possibly rims, what's the difference between a CX bike and a standard road racing cycle? Is it just the XC frame being slightly heavier and stronger? I know little about geometry beyond the obvious difference you see in MTB, Hybrid, road.

it's been covered alot here...brakes, tire clearance, knobbier tires, gearing...quite a bit actually, esp. as the competing level goes up. the experts here will better clarify. but the search function here is a real beauty! :)

Fractional rig. Wait! Wrong forum.

If you try to ride a cyclocross bike on the road, it explodes.

Check wikipedia.