Descriptor

1. In information retrieval, a word, similar to an index entry in a book, that identifies a significant topic or element in a stored document or group of documents. It is used as a key in rapid search and retrieval of information.
2. In programming, a piece of stored information used to describe something else, often in terms of structure, content, or some other property

Sources:

⠀ Microsoft Computer Dictionary.--5th ed Edition Microsoft Press 2002 – 648 c. – 648