The Collaborative International Dictionary of English v.0.48:

Moderation \Mod`er*a"tion\, n. [L. moderatio: cf. F.
   mod['e]ration.]
   1. The act of moderating, or of imposing due restraint.
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   2. The state or quality of being mmoderate.
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            In moderation placing all my glory,
            While Tories call me Whig, and Whigs a Tory. --Pope.
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   3. Calmness of mind; equanimity; as, to bear adversity with
      moderation.
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            The calm and judicious moderation of Orange.
                                                  --Motley.
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   4. pl. The first public examinations for degrees at the
      University of Oxford; -- usually contracted to mods.
      [1913 Webster]

WordNet (r) 3.0 (2006):

moderation
    n 1: quality of being moderate and avoiding extremes [syn:
         moderation, moderateness] [ant: immoderateness,
         immoderation]
    2: a change for the better [syn: easing, moderation,
       relief]
    3: the trait of avoiding excesses [syn: temperance,
       moderation] [ant: intemperance]
    4: the action of lessening in severity or intensity; "the object
       being control or moderation of economic depressions" [syn:
       moderation, mitigation]

Moby Thesaurus II by Grady Ward, 1.0:

56 Moby Thesaurus words for "moderation":
   abnegation, boundary, bounds, center, compromise, confinement,
   constraint, continence, denial, discipline, fence, forbearance,
   frugality, golden mean, gravity, half measures,
   half-and-half measures, halfway measures, happy medium, limit,
   limitation, mean, measure, medium, middle course, middle ground,
   middle way, moderateness, neutral ground, nothing in excess,
   prescription, proscription, qualification, renouncement,
   renunciation, restrain, restraint, restriction, sedateness,
   self-control, self-denial, self-discipline, self-mastery,
   self-restraint, seriousness, sober-mindedness, soberness,
   sobersidedness, sobersides, sobriety, solemnity, sophrosyne,
   staidness, temperance, temperateness, via media