Data about the structure of the data in a database.
1. Data about data. For example, the title, subject, author, and size of a file constitute metadata about the file. See also data dictionary, repository.
2. In the Microsoft .NET Framework, information that describes every element managed by the runtime: an assembly, loadable file, type, method, and so on. This can include information required for debugging and garbage collection, as well as security attributes, marshaling data, extended class and member definitions, version binding, and other information required by the runtime.
Meta-data, meta data
A repository of class definitions, each of which describes a specific class.