The Collaborative International Dictionary of English v.0.48:

Momus \Mo"mus\, prop. n. [Gr. ? blame, ridicule, Momus.] (Gr.
   Myth.)
   The god of mockery and censure.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Momus
    n 1: god of blame and mockery [syn: Momus, Momos]