The Collaborative International Dictionary of English v.0.48:

Orthography \Or*thog"ra*phy\, n. [OE. ortographie, OF.
   orthographie, L. orthographia, Gr. ?, fr. ? writing
   correctly; 'orqo`s right + gra`fein to write. See Ortho-,
   and Graphic.]
   [1913 Webster]
   1. The art or practice of writing words with the proper
      letters, according to standard usage; conventionally
      correct spelling; also, mode of spelling; as, his
      orthography is vicious.
      [1913 Webster]

            When spelling no longer follows the pronunciation,
            but is hardened into orthography.     --Earle.
      [1913 Webster]

   2. The part of grammar which treats of the letters, and of
      the art of spelling words correctly.
      [1913 Webster]

   3. A drawing in correct projection, especially an elevation
      or a vertical section.
      [1913 Webster]

   4. The method of spelling the words of a particular language;
      the system of symbols used for writing a language.
      [PJC]

   5. The branch of linguistics concerned with how languages are
      written.
      [PJC]

WordNet (r) 3.0 (2006):

orthography
    n 1: a method of representing the sounds of a language by
         written or printed symbols [syn: orthography, writing
         system]

The Devil's Dictionary (1881-1906):

ORTHOGRAPHY, n.  The science of spelling by the eye instead of the
ear.  Advocated with more heat than light by the outmates of every
asylum for the insane.  They have had to concede a few things since
the time of Chaucer, but are none the less hot in defence of those to
be conceded hereafter.

    A spelling reformer indicted
    For fudge was before the court cicted.
        The judge said:  "Enough --
        His candle we'll snough,
    And his sepulchre shall not be whicted."