The time required for the amplitude of a pulse to decrease (fall) from a specified value (usually 90 percent of the peak value exclusive of overshoot or undershoot) to another specified value (usually 10 percent of the peak value exclusive of overshoot or undershoot. ) Note: Limits on undershoot and oscillation, i.e., hunting, may need to be specified when specifying fall time limits. Synonym pulse decay time.