How about ... signal is that property of a WikiPage that prevents its deletion?
A circular definition, but CircularDefinitionsCanBeValid?, e.g. PageRank.
A communication term used to signify a ratio between intelligent signal and random static in a received transmission containing both.
Thus useful in rating pages on a wiki, where objective facts and subjective opinions are mixed in the received transmission. But can also be applied where the noise signal is confusing and unclear, or not to the point as in ConversationalChaff.
Signal refers to the content of a wiki page that is directly related to the WikiName and/or the relation of the page to the Wiki as a whole (e.g., category links).
Signal is the useful/usable content of a page. This will sometimes not seem to relate directly to the PageName, but nonetheless provides useful content and/or context.