(also cypher), n.A technique to convert information (plaintext) into a form that is unintelligible (ciphertext) without knowing the rules (algorithm) to convert it back to its original form.A message that is so encoded; synonymous with ciphertext.A key that is used to convert the plaintext to ciphertext.A design of interlacing initials; also cypher monogram.


Cipher4 monograms frequently appear on the backs of 19th-century cartes-de-visite and cabinet cards.