The Collaborative International Dictionary of English v.0.48:

Lexicography \Lex`i*cog"ra*phy\
   (l[e^]ks`[i^]*k[o^]g"r[.a]*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; as, with so many words lexicography can be
   interesting in parts but at length is rather tedious labor.
   [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

lexicography
    n 1: the act of writing dictionaries