The Collaborative International Dictionary of English v.0.48:

Comparative \Com*par"a*tive\, n. (Gram.)
   The comparative degree of adjectives and adverbs; also, the
   form by which the comparative degree is expressed; as,
   stronger, wiser, weaker, more stormy, less windy, are all
   comparatives.
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         In comparatives is expressed a relation of two; as in
         superlatives there is a relation of many. --Angus.
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   2. An equal; a rival; a compeer. [Obs.]
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            Gerard ever was
            His full comparative.                 --Beau. & Fl.
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   3. One who makes comparisons; one who affects wit. [Obs.]
      "Every beardless vain comparative." --Shak.
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The Collaborative International Dictionary of English v.0.48:

Comparative \Com*par"a*tive\, a. [L. comparativus: cf. F.
   comparatif.]
   1. Of or pertaining to comparison. "The comparative faculty."
      --Glanvill.
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   2. Proceeding from, or by the method of, comparison; as, the
      comparative sciences; the comparative anatomy.
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   3. Estimated by comparison; relative; not positive or
      absolute, as compared with another thing or state.
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            The recurrence of comparative warmth and cold.
                                                  --Whewell.
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            The bubble, by reason of its comparative levity to
            the fluid that incloses it, would necessarily ascend
            to the top.                           --Bentley.
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   4. (Gram.) Expressing a degree greater or less than the
      positive degree of the quality denoted by an adjective or
      adverb. The comparative degree is formed from the positive
      by the use of -er, more, or less; as, brighter, more
      bright, or less bright.
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   Comparative sciences, those which are based on a
      comprehensive comparison of the range of objects or facts
      in any branch or department, and which aim to study out
      and treat of the fundamental laws or systems of relation
      pervading them; as, comparative anatomy, comparative
      physiology, comparative philology.
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WordNet (r) 3.0 (2006):

comparative
    adj 1: relating to or based on or involving comparison;
           "comparative linguistics"
    2: estimated by comparison; not absolute or complete; "a
       relative stranger" [syn: relative, comparative] [ant:
       absolute]
    n 1: the comparative form of an adjective or adverb; "`faster'
         is the comparative of the adjective `fast'"; "`less famous'
         is the comparative degree of the adjective `famous'";
         "`more surely' is the comparative of the adverb `surely'"
         [syn: comparative, comparative degree]

Moby Thesaurus II by Grady Ward, 1.0:

33 Moby Thesaurus words for "comparative":
   affinitive, analogical, analogous, appertaining, approximate,
   associative, collatable, commensurable, commensurate, comparable,
   congenial, connective, correlative, en rapport, equivalent, like,
   linking, matchable, much at one, near, parallel, pertaining,
   pertinent, proportionable, proportional, proportionate, referable,
   referring, relating, relational, relative, similar, sympathetic