1. The complete set of signals, usually electromagnetic or acoustic, received from a source such as an infrared object, a radio or radar transmitter, an aircraft, or a ship. Note: Signatures may consist of analog or digital signals, or both, and may be analyzed to indicate the nature of their source and assist in its recognition. 2. The attributes of an electromagnetic or acoustic wave that has been reflected from or transmitted through an object and contains information indicating the attributes of the object. Note: In this context, "objects" may include man-made objects or natural ones, the latter including both those that are well defined, e.g., terrain, and those that are not, e.g., weather phenomena. See also digital signature.