DAU - Information describing the characteristics of data, data or information about data, or descriptive information about an entitys data, data activities, systems, and holdings. For example, discovery metadata is a type of metadata that allows data assets to be found using enterprise search capabilities. Metadata can be structural (specifying the format structure), semantic (specifying the meaning), or descriptive (providing amplifying or interpretive information) for data, information, or IT services.

MIL-STD-31000B - Data that provides information about other data. For the purpose of this standard, metadata is defined to be data about a design and/or engineering design documents. (Part number, drawing number, nomenclature, revision, date approved, approved by, used on, etc., are examples of metadata). Metadata is used by the design and procuring activities to store, manage, and provide access to TDP elements.

NAS 9300-007 - The data required for the management and use of information packages.

Action Engineering - Data that supports the definition, administrative, or supplemental data package. Metadata includes all relations, parameters, and system information used in a model. This data resides at the model and feature level.