The Collaborative International Dictionary of English v.0.48:

cosmology \cos*mol"o*gy\ (k[o^]z*m[o^]l"[-o]*j[y^]), n. [Gr.
   ko`smos the world + -logy: cf. F. cosmologie.]
   1. The branch of science or philosophy dealing with the
      origin and nature of the universe as a whole. specifically
      (a) (Philosophy) the branch of metaphysics speculating on
          the structure and nature of the most fundamental parts
          of the system of creation, such as space and time, the
          elements of bodies, the structure of the universe, the
          modifications of material things, causality, the laws
          of motion, and the order and course of nature.
      (b) (Astronomy) the branch of astronomy dealing with the
          origin and structure of the universe, including the
          evolution of its present observable structure, using
          the methods of observational astronomy as well as
          mathematical physics.
          [1913 Webster +PJC]

   2. a treatise dealing with the original and structure of the
      universe.
      [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

cosmology
    n 1: the metaphysical study of the origin and nature of the
         universe
    2: the branch of astrophysics that studies the origin and
       evolution and structure of the universe [syn: cosmology,
       cosmogony, cosmogeny]

Moby Thesaurus II by Grady Ward, 1.0:

39 Moby Thesaurus words for "cosmology":
   aesthetics, astrogony, axiology, big bang theory, casuistry,
   continuous creation theory, cosmic evolution, cosmic philosophy,
   cosmism, cosmogony, cosmography, epistemology, ethics,
   expanding universe theory, first philosophy, gnosiology, logic,
   mental philosophy, metaphysics, moral philosophy,
   nebular hypothesis, ontology, phenomenology, philosophastry,
   philosophic doctrine, philosophic system, philosophic theory,
   philosophical inquiry, philosophical speculation, philosophy,
   pulsating universe theory, school of philosophy, school of thought,
   science of being, sophistry, stellar cosmogony, theory of beauty,
   theory of knowledge, value theory