[from analog electronics]
n. Used by hackers in a generalization of its technical meaning. 'Signal' refers to useful information conveyed by some communications medium, and 'noise' to anything else on that medium. Hence a low ratio implies that it is not worth paying attention to the medium in question. Figures for such metaphorical ratios are never given. The term is most often applied to USENET newsgroups during flame wars.
See also coefficient of X, S/N Ratio, lost in the noise.