meta
<philosophy> /me't*/ or /may't*/ or (Commonwealth) /mee't*/ A prefix meaning one level of description higher. If X is some concept then meta-X is data about, or processes operating on, X.

A metasyntactic variable [http://www.nightflight.com/cgi-bin/foldoc.cgi?metasyntactic+variable] (e.g. FOO) is a variable in notation used to describe syntax, and MetaLanguage is a language used to describe language (e.g. BNF).

For example, a metasyntax is syntax for specifying syntax, metalanguage is a language used to discuss language, meta-data is data about data, and meta-reasoning is reasoning about reasoning.

MetaData is "data about data."
IE: Data that the system uses to determine how other data is processed.

This is difficult to explain briefly, but much hacker humour turns on deliberate confusion between meta-levels.

(The above is primarily from FOLDOC, the FreeOnLineDictionaryOfComputing at http://wombat.doc.ic.ac.uk/foldoc/foldoc.cgi?query=meta&action=Search)
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Some more down to earth examples:
*meta thinking is thinking about thinking
*a meta plan is a plan about planning
*a meta discussion is a discussion about discussion
*meta processing is processing of processes
Hmm, writing this it looks to me, that this is rather the format "meta-X is X about X", not "meta-X is data about X". Either these are two readings of "meta" or the data must have a special quality or the candidates for X must be data.

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