1. The deterioration in quality, level, or standard of performance of a functional unit.
Note: Degradation is usually categorized as either "graceful" or "catastrophic."
Source: from Federal Standard 1037C
There are several forms and causes of degradation in electric signals, both in the time domain and in the physical domain: runt pulse, spike, jitter, wander, swim, drift, glitch, ringing, crosstalk, antenna effect, phase noise