Bump steer occurs when your vehicle pulls to one side or another after you have hit a road irregularity like a pot hole. It always happens after the wheel rebounds (jounce).
Bump steer is the same whether in reference to an SUV or any other vehicle. In simplest terms it is when, after hitting a bump, the car steers even when the driver intends to go straight and actually holds the steering wheel straight.
It is caused because the suspension of vehicles are somewhat complicated and there are many adjustments. These adjustments are all done so that when the vehicle is sitting (or more correctly driving) normally it goes straight forward. When bumps are big enough to cause much of the weight of the vehicle to bounce enough that weight is taken off the suspension, these finely tuned adjustments are no longer accurate. This causes a temporary "turn" in one direction or another.