The Collaborative International Dictionary of English v.0.48:

Cipher \Ci"pher\, a.
   Of the nature of a cipher; of no weight or influence. "Twelve
   cipher bishops." --Milton.
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The Collaborative International Dictionary of English v.0.48:

Cipher \Ci"pher\, v. i. [imp. & p. p. Ciphered; p. pr. & vb.
   n. Ciphering.]
   To use figures in a mathematical process; to do sums in
   arithmetic.
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         'T was certain he could write and cipher too.
                                                  --Goldsmith.
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The Collaborative International Dictionary of English v.0.48:

Cipher \Ci"pher\, v. t.
   1. To write in occult characters.
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            His notes he ciphered with Greek characters.
                                                  --Hayward.
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   2. To get by ciphering; as, to cipher out the answer.
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   3. To decipher. [Obs.] --Shak.
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   4. To designate by characters. [Obs.] --Shak.
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The Collaborative International Dictionary of English v.0.48:

Cipher \Ci"pher\, n. [OF. cifre zero, F. Chiffre figure (cf.
   Sp.cifra, LL. cifra), fr. Ar. [,c]ifrun, [,c]afrun, empty,
   cipher, zero, fr. [,c]afira to be empty. Cf. Zero.]
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   1. (Arith.) A character [0] which, standing by itself,
      expresses nothing, but when placed at the right hand of a
      whole number, increases its value tenfold.
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   2. One who, or that which, has no weight or influence.
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            Here he was a mere cipher.            --W. Irving.
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   3. A character in general, as a figure or letter. [Obs.]
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            This wisdom began to be written in ciphers and
            characters and letters bearing the forms of
            creatures.                            --Sir W.
                                                  Raleigh.
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   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.
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   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.
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            His father . . . engaged him when he was very young
            to write all his letters to England in cipher. --Bp.
                                                  Burnet.
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   Cipher key, a key to assist in reading writings in cipher.
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WordNet (r) 3.0 (2006):

cipher
    n 1: a message written in a secret code [syn: cipher,
         cypher]
    2: a mathematical element that when added to another number
       yields the same number [syn: zero, 0, nought, cipher,
       cypher]
    3: a quantity of no importance; "it looked like nothing I had
       ever seen before"; "reduced to nil all the work we had done";
       "we racked up a pathetic goose egg"; "it was all for naught";
       "I didn't hear zilch about it" [syn: nothing, nil, nix,
       nada, null, aught, cipher, cypher, goose egg,
       naught, zero, zilch, zip, zippo]
    4: a person of no influence [syn: cipher, cypher, nobody,
       nonentity]
    5: a secret method of writing [syn: cipher, cypher,
       cryptograph, secret code]
    v 1: convert ordinary language into code; "We should encode the
         message for security reasons" [syn: code, encipher,
         cipher, cypher, encrypt, inscribe, write in code]
    2: make a mathematical calculation or computation [syn:
       calculate, cipher, cypher, compute, work out,
       reckon, figure]

Moby Thesaurus II by Grady Ward, 1.0:

175 Moby Thesaurus words for "cipher":
   Aesopian language, Babel, Greek, John Hancock, X, a nobody,
   a nothing, add, algebraize, allegory, alphabetic character, argot,
   aught, autograph, babble, binary digit, bit, break, calculate,
   cant, cast, character, charactery, christcross, clear up, code,
   coded message, common man, compute, conventional symbol,
   countermark, countersign, countersignature, counterstamp, cross,
   cryptoanalysis, cryptoanalytics, cryptogram, cryptograph,
   cryptographer, cryptography, decipher, device, digit, divide,
   dope out, double Dutch, dud, dummy, emblem, encipher, encode,
   endorsement, estimate, extract roots, figure, figure in,
   figure out, figurehead, garble, gibberish, gift of tongues,
   glossolalia, gobbledygook, goose egg, graph, grapheme, hand,
   hollow man, iconology, ideogram, initials, insignificancy, integer,
   invisible ink, jackstraw, jargon, jumble, lay figure, letter,
   lexigraphic character, lightweight, little fellow, little guy,
   logogram, logotype, love knot, man of straw, mark,
   mark of signature, measure, mediocrity, monogram, multiply, nada,
   naught, nebbish, nichts, nihil, nil, nix, no such thing, nobody,
   nobody one knows, noise, nonentity, notation, nothing,
   nothing at all, nothing on earth, nothing whatever, nullity,
   number, numeral, numero, obscurity, phonetic character,
   phonetic symbol, pictogram, pictographic character, pip-squeak,
   punk, puppet, pushover, puzzle out, reckon, resolve, runt, score,
   scramble, scrub, seal, secret language, secret writing, shrimp,
   sigil, sign, sign manual, signature, signet, slang, small fry,
   small potato, small potatoes, squirt, squit, subscription,
   subtract, syllabic, symbol, symbolic system, symbolism,
   symbolization, symbology, sympathetic ink, take account of, tally,
   thing of naught, token, totem, totem pole, trifle, type, unravel,
   unriddle, visa, vise, whiffet, whippersnapper, whole number,
   work out, writing, written character, zero, zilch



Bouvier's Law Dictionary, Revised 6th Ed (1856):

CIPHER. An arithmetical character, used for numerical notation. Vide
Figures, and 13 Vin. Ab. 210; 18 Eng. C. L. R. 95; 1 Ch. Cr. Law, 176.
     2. By cipher is also understood a mode of secret writing. Public
ministers and other public agents frequently use ciphers in their
correspondence, and it is sometimes very useful so to correspond in times of
war. A key is given to each minister before his departure, namely, the
cipher for writing ciphers, (chiffre chiffrant,) and the cipher for
deciphering (chiffre dechiffrant.) Besides these, it is usual to give him a
common cipher, (chiffre banal,) which is known to all the ministers of the
same power, who occasionally use it in their correspondence with each other.
     3. When it is suspected that, a cipher becomes known to the cabinet
where the minister is residing, recourse is had to a preconcerted sign in
order to annul, entirely or in part, what has been written in cipher, or
rather to indicate that the contents are to be understood in an inverted or
contrary sense. A cipher of reserve is also employed in extraordinary cases.