The Collaborative International Dictionary of English v.0.48:

Comparison \Com*par"i*son\ (? or ?), n. [F. comparaison, L.
   comparatio. See 1st Compare.]
   1. The act of comparing; an examination of two or more
      objects with the view of discovering the resemblances or
      differences; relative estimate.
      [1913 Webster]

            As sharp legal practitioners, no class of human
            beings can bear comparison with them. --Macaulay.
      [1913 Webster]

            The miracles of our Lord and those of the Old
            Testament afford many interesting points of
            comparison.                           --Trench.
      [1913 Webster]

   2. The state of being compared; a relative estimate; also, a
      state, quality, or relation, admitting of being compared;
      as, to bring a thing into comparison with another; there
      is no comparison between them.
      [1913 Webster]

   3. That to which, or with which, a thing is compared, as
      being equal or like; illustration; similitude.
      [1913 Webster]

            Whereto shall we liken the kingdom of God? Or with
            what comparison shall we compare it?  --Mark iv. 30.
      [1913 Webster]

   4. (Gram.) The modification, by inflection or otherwise,
      which the adjective and adverb undergo to denote degrees
      of quality or quantity; as, little, less, least, are
      examples of comparison.
      [1913 Webster]

   5. (Rhet.) A figure by which one person or thing is compared
      to another, or the two are considered with regard to some
      property or quality, which is common to them both; e.g.,
      the lake sparkled like a jewel.
      [1913 Webster]

   6. (Phren.) The faculty of the reflective group which is
      supposed to perceive resemblances and contrasts.
      [1913 Webster]

   Beyond comparison, so far superior as to have no likeness,
      or so as to make comparison needless.

   In comparison of, In comparison with, as compared with;
      in proportion to. [Archaic] "So miserably unpeopled in
      comparison of what it once was." --Addison.

   Comparison of hands (Law), a mode of proving or disproving
      the genuineness of a signature or writing by comparing it
      with another proved or admitted to be genuine, in order to
      ascertain whether both were written by the same person.
      --Bouvier. --Burrill.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Comparison \Com*par"i*son\, v. t.
   To compare. [Obs.] --Wyclif.
   [1913 Webster]

WordNet (r) 3.0 (2006):

comparison
    n 1: the act of examining resemblances; "they made a comparison
         of noise levels"; "the fractions selected for comparison
         must require pupils to consider both numerator and
         denominator" [syn: comparison, comparing]
    2: relation based on similarities and differences
    3: qualities that are comparable; "no comparison between the two
       books"; "beyond compare" [syn: comparison, compare,
       equivalence, comparability]

Moby Thesaurus II by Grady Ward, 1.0:

98 Moby Thesaurus words for "comparison":
   accordance, affinity, agent, agreement, alikeness, alliance,
   alternate, alternative, analogy, aping, approach, approximation,
   assimilation, backup, balance, balancing, change, changeling,
   closeness, commensurability, community, comparability, conformity,
   contrast, contrasting, copy, copying, correspondence, counterfeit,
   deputy, double, dummy, equal, equivalent, ersatz, exchange, fake,
   fill-in, ghost, ghostwriter, identity, imitation, juxtaposing,
   juxtaposition, kinship, likeness, likening, locum tenens,
   makeshift, match, metaphor, metonymy, mimicking, nearness,
   next best thing, parallelism, parity, personnel, phony,
   pinch hitter, proxy, relation, relationship, relief, replacement,
   representative, resemblance, reserves, ringer, sameness,
   second string, secondary, semblance, sign, similarity, simile,
   similitude, simulation, spares, stand-in, sub, substituent,
   substitute, substitution, succedaneum, superseder, supplanter,
   surrogate, symbol, synecdoche, third string, token, understudy,
   utility player, vicar, vice-president, vice-regent, weighing