A cipher or cryptogram.
A device used for encrypting or decrypting text.
To write text using a code or cipher.
Any word used as the key to a code.
A reserved word used to identify a specific command, function, etc.
Any important word in a text or document, which may be linked to other words or other information, or at least merely listed in the metadata for searches to find.
Any word that occurs in a text more often than normal.
Any word used in a reference work to link to other words or other information.
To tag with keywords, as for example to facilitate searching.