The Collaborative International Dictionary of English v.0.48:

Homomorphism \Ho`mo*mor"phism\, n. [See Homomorphous.]
   1. (Biol.) Same as Homomorphy.
      [1913 Webster]

   2. (Bot.) The possession, in one species of plants, of only
      one kind of flowers; -- opposed to heteromorphism,
      dimorphism, and trimorphism.
      [1913 Webster]

   3. (Zool.) The possession of but one kind of larv[ae] or
      young, as in most insects.
      [1913 Webster]

WordNet (r) 3.0 (2006):

homomorphism
    n 1: similarity of form [syn: homomorphism, homomorphy]

The Free On-line Dictionary of Computing (30 December 2018):

homomorphism

    A map f between groups A and B is a
   homomorphism of A into B if

    f(a1 * a2) = f(a1) * f(a2)  for all a1, a2 in A.

   where the *s are the respective group operations.

   (2009-01-14)