Bump steer would be bump doing the steering. What do you see it as the meaning?
Bump steer is when the toe changes as a result of vertical wheel movement. It's a function of the suspension and steering geometry, so a car can't have "terrible bump steer, and god-like bump-steer in a single package". That's just rubbish, I'm afraid. A car (unless you crash it, of course) will have the same bump-steer characteristics as when it left the factory, for the whole of its life.
On front suspension, it is typically caused by the track rod end tracing a different path to the axle centre, as the suspension moves up and down. So, in a double-wishbone setup, for example, the centre of the stub axle will describe an arc between full rebound and full bump. If the steering rack has been correctly designed and positioned, the track rod will describe the same arc, as closely as possible. Unfortunately, it is almost impossible to get zero bump-steer, because the track rod describes part of a circle as it moves (the centre being at the centre of the inner balljoint, and the circumference being traced by the centre of the track rod end). But the wishbones, being of unequal length, won't describe a circle. The trick, therefore, is to try and get the best possible match between the two arcs, between mid-laden and full bump. It matters less as you get further into rebound, because the tyre isn't contributing much grip in that condition.
Other suspension arrangements will have their own bump-steer characteristics. So, for example, a live axle on leaf springs, will steer very slightly, as the spring lengthens and shortens between full rebound, mid-laden and full bump. Semi-trailing arms will bump-steer, by their nature - and at the rear of the car, the manufacturer might make it deliberately so, in order to get the handling characteristics he's looking for.
The point, however, is that these are all inherent in the design of the car. There's nothing you can do with initial toe settings that will make any appreciable difference to the bump-steer characteristics. Moving the steering rack up and down slightly, is about the only practicable thing you can do. Some mounting arrangements lend themselves to that, better than others. I've never come across a car that has had bump-steer so bad, that an inch of suspension travel either side of mid-laden, has made a noticeable difference to how the car feels.
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