What does "cipher" mean?

Additional senses

1. 2.A character in general, as a figure or letter. [Obs.] This wisdom began to be written in ciphers and characters and letters bearing the forms of creatures. Sir W. Raleigh.
2. 3.A combination or interweaving of letters, as the initials of a name; a device; a monogram; as, a painter's cipher, an engraver's cipher, etc. The cut represents the initials N. W.
3. 4.A private alphabet, system of characters, or other mode of writing, contrived for the safe transmission of secrets; also, a writing in such characters. His father . . . engaged him when he was very young to write all his letters to England in cipher. Bp. Burnet. Cipher key, a key to assist in reading writings in cipher.
4. 5.Of the nature of a cipher; of no weight or influence. "Twelve cipher bishops." Milton.
5. 6.To use figures in a mathematical process; to do sums in arithmetic. "T was certain he could write and cipher too. Goldsmith.
6. 7.To write in occult characters. His notes he ciphered with Greek characters. Hayward.
7. 8.To get by ciphering; as, to cipher out the answer.
8. 9.To decipher. [Obs.] Shak.
9. 10.To designate by characters. [Obs.] Shak.