ci·pher / ˈsīfər/ (also cy·pher) • n. 1. a secret or disguised way of writing; a code: he was writing cryptic notes in a cipher | the information may be given in cipher. ∎  a thing written in such a code. ∎  a key to such a code.2. dated a zero; a figure 0. ∎ fig. a person or thing of no importance, esp. a person who does the bidding of others and seems to have no will of their own.3. a monogram.4. a continuous sounding of an organ pipe, caused by a mechanical defect.• v. 1. [tr.] put (a message) into secret writing; encode.2. [intr.] archaic do arithmetic.

cipher, cypher
A. .(arith.) symbol by itself denoting ‘nothing’ XIV; nonentity; Arabic numeral XVI;

B. .secret manner of writing; †hieroglyph XVI; literal device, monogram XVII;

C. .continuous sounding of a note on an organ due to mechanical defect XVIII. ME. siphre, sipher — OF. sif(f)re (mod. chiffre) — medL. cif(e)ra, partly through It. cifra, †cifera f. Arab. ṣifr ZERO, sb. use of adj. ‘empty’, f. ṣafira be empty.
Hence as vb. work sums; write in cipher. XVI. Cf. DECIPHER.

cipher
1. An algorithm employed for encryption, or, in its inverse form, for decryption. See cryptography.

2. An encrypted message.

cipher a secret or disguised way of writing; a code. The term comes (in late Middle English, in the senses ‘symbol for zero’ and ‘arabic numeral’) from Old French, based on Arabic ṣifr ‘zero’.

cipher See cryptography