Non-linear, for those not of the math sort, can be translated in a number of ways. One is 'not on
a straight line' While it's good to be able to turn, it is rather desirable that you also be able
to do this. More often, this might be taken as a sign that when you change something, you'll find
that the amount of reaction in it will vary a great deal.|
Another alternative is that you aren't traveling on a line at all.
The most famous vehicle of that design appears in The Hitchhiker's Guide to the Galaxy.