What is bump steer?
 

I did some research and found this meaning "occurs when the steering angle of the front wheels changes as the suspension moves up and down through its range of travel. Generally speaking, Bump Steer is undesirable.
"

However, how do you know if you have it? What will your car/truck do. How do you know if its another issue?

Thanks.

Here maybe this will help:

http://www.bakerprecision.com/longacr17a.htm

Here's an easy test, place your buggy/truck on a flat surface. Now press straight down on the front of your buggy/truck, as the suspension compresses, do your wheels move left or right? If so that is bump steer at work. Same thing can happen in the rear as well.