1. Any function, often of time but possibly of any variable, with a substantial lack of correlation between values at successive times. For example, the autocorrelation function of white noise is a sharp spike: Its value at any instant is correlated only with its value at that instant. 2. Any change in a signal that degrades its capability to transmit information (e.g., the audible static on AM radio resulting from lightning discharges). 3. See meteorological noise.