In general terms, when mathematically describing the transition of any parameter from a lower value to a higher value, overshoot occurs when the value of the transition is higher than the final value. Visually, you can think of it as a peak in between and rising above two points of differing heights. Conversely, undershoot occurs when the transition is from higher to lower, and it’s value is lower than the final value.
In electronics, overshoot is the increased amplitude of a portion of a signal at the output of a non-linear circuit, such as an amplifier. Overshoot can cause distortion, and may result from design parameters intended to decrease the response time of the circuit. The presence (or absence) of overshoot and its magnitude is a function of a circuit design parameter known as damping. In the case of the Sony Oxford Transient Modulator plug-in, overshoot is intentionally used as a controllable parameter to either enhance or attenuate transients in program material (see tech tip: 4-6-06).