RhymeZone: keyword definitions

Definitions of keyword:

noun: (cryptography) Any word used as the key to a code.
noun: (information science) Any word used in a reference work to link to other words or other information.
noun: (programming) A reserved word used to identify a specific command, function, etc.
noun: (linguistics) Any word that occurs in a text more often than normal.
verb: (transitive) To tag with keywords, as for example to facilitate searching.

(Definitions from Wiktionary)