:signal-to-noise ratio: [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 war}s.
Compare {bandwidth}. See also {coefficient of X}, {lost in
the noise}.
-- The AI Hackers Dictionary