Source : Webster's Revised Unabridged Dictionary (1913)

Lexicography \Lex`i*cog"ra*phy\ (-f[y^]), n. [Cf. F.
   lexicographie.]
   The art, process, or occupation of making a lexicon or
   dictionary; the principles which are applied in making
   dictionaries.

Source : WordNet®

lexicography
     n : the act of writing dictionaries