ADJECTIVE (2)

1. having the same evolutionary origin but not necessarily the same function;
- Example: "the wing of a bat and the arm of a man are homologous"

2. corresponding or similar in position or structure or function or characteristics; especially derived from an organism of the same species;
- Example: "a homologous tissue graft"

The Collaborative International Dictionary of English v.0.48:

Homologous \Ho*mol"o*gous\, a. [Gr. ? assenting, agreeing; ? the
   same + ? speech, discourse, proportion, ? to say, speak.]
   Having the same relative position, proportion, value, or
   structure. Especially:
   (a) (Geom.) Corresponding in relative position and
       proportion.
       [1913 Webster]

             In similar polygons, the corresponding sides,
             angles, diagonals, etc., are homologous. --Davies &
                                                  Peck (Math.
                                                  Dict.).
   (b) (Alg.) Having the same relative proportion or value, as
       the two antecedents or the two consequents of a
       proportion.
   (c) (Chem.) Characterized by homology; belonging to the same
       type or series; corresponding in composition and
       properties. See Homology, 3.
   (d) (Biol.) Being of the same typical structure; having like
       relations to a fundamental type to structure; as, those
       bones in the hand of man and the fore foot of a horse are
       homologous that correspond in their structural relations,
       that is, in their relations to the type structure of the
       fore limb in vertebrates.
       [1913 Webster]

   Homologous stimulus. (Physiol.) See under Stimulus.
      [1913 Webster]

WordNet (r) 3.0 (2006):

homologous
    adj 1: having the same evolutionary origin but not necessarily
           the same function; "the wing of a bat and the arm of a
           man are homologous" [ant: analogous, heterologic,
           heterological, heterologous]
    2: corresponding or similar in position or structure or function
       or characteristics; especially derived from an organism of
       the same species; "a homologous tissue graft" [ant:
       autologous, heterologous]

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "homologous":
   analogous, answering, approximate, approximating, approximative,
   close, coequal, comparable, complemental, complementary,
   correspondent, corresponding, equipollent, equivalent, like, near,
   proximate, reciprocal, reciprocative, relatable, similar,
   tantamount