That depends on a number of things, such as what the original mathematical object represented and what you are taking the derivative with respect to. For instance, the second derivative of position with respect to time is acceleration, the third is jerk, and apparently the fourth is jounce (http://en.wikipedia.org/wiki/Jounce)..
well i think what he meant by jerk is just to explain the idea what would happen if the acceleration is also changes with time. try to think for real time situation..like driving a car...first derivative mean velocity,second means acceleration and then derivation of acceleration is jerk.so if u will the acceleration again and again u will have jerks...