Ci″pher (?), n. [OF. cifre zero, F. Chiffre figure (cf. Sp. cifra, LL. cifra), fr. Ar. çifrun, çafrun, empty, cipher, zero, fr. çafira to be empty. Cf. Zero.]
1. (Arith.) A character which, standing by itself, expresses nothing, but when placed at the right hand of a whole number, increases its value tenfold.
2. One who, or that which, has no weight or influence.
Here he was a mere cipher.
W. Irving.
3. A character in general, as a figure or letter.
This wisdom began to be written in ciphers and characters and letters bearing the forms of creatures.
Sir W. Raleigh.
4. 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.
5. 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.