The Collaborative International Dictionary of English v.0.48:

Conservative \Con*serv"a*tive\, n.
   1. One who, or that which, preserves from ruin, injury,
      innovation, or radical change; a preserver; a conserver.
      [1913 Webster]

            The Holy Spirit is the great conservative of the new
            life.                                 --Jer. Taylor.
      [1913 Webster]

   2. One who desires to maintain existing institutions and
      customs; also, one who holds moderate opinions in
      politics; -- opposed to revolutionary or radical.
      [1913 Webster]

   3. (Eng. Hist.) A member of the Conservative party.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Conservative \Con*serv"a*tive\, a. [Cf. F. conservatif.]
   1. Having power to preserve in a safe of entire state, or
      from loss, waste, or injury; preservative.
      [1913 Webster]

   2. Tending or disposed to maintain existing institutions;
      opposed to change or innovation.
      [1913 Webster]

   3. Of or pertaining to a political party which favors the
      conservation of existing institutions and forms of
      government, as the Conservative party in England; --
      contradistinguished from Liberal and Radical.
      [1913 Webster]

            We have always been conscientiously attached to what
            is called the Tory, and which might with more
            propriety be called the Conservative, party.
                                                  --Quart. Rev.
                                                  (1830).
      [1913 Webster]

   Conservative system (Mech.), a material system of such a
      nature that after the system has undergone any series of
      changes, and been brought back in any manner to its
      original state, the whole work done by external agents on
      the system is equal to the whole work done by the system
      overcoming external forces.                 --Clerk
                                                  Maxwell.
      [1913 Webster]

WordNet (r) 3.0 (2006):

conservative
    adj 1: resistant to change [ant: liberal]
    2: having social or political views favoring conservatism
    3: avoiding excess; "a conservative estimate" [syn: cautious,
       conservative]
    4: unimaginatively conventional; "a colorful character in the
       buttoned-down, dull-grey world of business"- Newsweek [syn:
       button-down, buttoned-down, conservative]
    5: conforming to the standards and conventions of the middle
       class; "a bourgeois mentality" [syn: bourgeois,
       conservative, materialistic]
    n 1: a person who is reluctant to accept changes and new ideas
         [syn: conservative, conservativist] [ant: liberal,
         liberalist, progressive]
    2: a member of a Conservative Party

Moby Thesaurus II by Grady Ward, 1.0:

139 Moby Thesaurus words for "conservative":
   Bircher, Bourbon, Epistle side, Methuselah, Tory, antediluvian,
   antique, back number, backward, bitter-ender, careful, cautious,
   centrist, chary, circumspect, clockwise, compromiser, conformist,
   conservational, conservationist, conservatist, conservatory,
   conserving, controlled, conventional, dad, decanal side, dexter,
   dextral, dextrocardial, dextrocerebral, dextrocular, dextrogyrate,
   dextrogyratory, dextropedal, dextrorotary, dextrorse, die-hard,
   diehard, discreet, dodo, elder, extreme right-winger, fogy,
   fogyish, fossil, fud, fuddy-duddy, fundamentalist, granny,
   hard hat, has-been, hidebound, imperialist, keeping,
   laudator temporis acti, longhair, matriarch, mid-Victorian,
   middle-of-the-road, middle-of-the-roader, moderate, moderationist,
   moderatist, monarchist, mossback, neutral, nonprogressive, off,
   old believer, old crock, old dodo, old fogy, old liner, old man,
   old poop, old school, old woman, old-fashioned, old-fogyish,
   old-line, old-timer, opposed to change, orthodox, patriarch,
   politic, pop, pops, preservative, preservatory, preserving, proper,
   protective, prudent, radical right, reactionarist, reactionary,
   reactionist, reasonable, recto, regular old fogy, relic,
   restrained, right, right field, right hand, right of center,
   right side, right wing, right-hand, right-wing, right-winger,
   right-wingish, rightist, royalist, saving, sober, social Darwinist,
   square, stable, standard, standpat, standpatter, starboard,
   starboard tack, starets, stick-in-the-mud, temperate, tory,
   traditional, traditionalist, traditionalistic, true-blue,
   ultraconservative, unexcessive, unextravagant, unextreme,
   unprogressive, wary



Moby Thesaurus II by Grady Ward, 1.0:

19 Moby Thesaurus words for "Conservative":
   Democrat, Labourite, Republican, Tory, Whig, heeler, loyalist,
   partisan, party faithful, party hack, party man, party member,
   party wheelhorse, registered Democrat, registered Republican,
   regular, stalwart, ward heeler, wheelhorse



The Devil's Dictionary (1881-1906):

CONSERVATIVE, n.  A statesman who is enamored of existing evils, as
distinguished from the Liberal, who wishes to replace them with
others.