The Collaborative International Dictionary of English v.0.48:

Prudence \Pru"dence\, n. [F., fr. L. prudentia, contr. from
   providentia. See Prudent, and cf. Providence.]
   The quality or state of being prudent; wisdom in the way of
   caution and provision; discretion; carefulness; hence, also,
   economy; frugality.
   [1913 Webster]

         Prudence is principally in reference to actions to be
         done, and due means, order, seasons, and method of
         doing or not doing.                      --Sir M. Hale.
   [1913 Webster]

         Prudence supposes the value of the end to be assumed,
         and refers only to the adaptation of the means. It is
         the relation of right means for given ends. --Whewell.
   [1913 Webster]

   Syn: Wisdom; forecast; providence; considerateness;
        judiciousness; discretion; caution; circumspection;
        judgment. See Wisdom.
        [1913 Webster]

WordNet (r) 3.0 (2006):

prudence
    n 1: discretion in practical affairs [ant: imprudence]
    2: knowing how to avoid embarrassment or distress; "the servants
       showed great tact and discretion" [syn: discretion,
       discreetness, circumspection, prudence]

Moby Thesaurus II by Grady Ward, 1.0:

224 Moby Thesaurus words for "prudence":
   abnegation, abstinence, acumen, advantage, advantageousness,
   advisability, anticipation, appropriateness, astuteness, austerity,
   austerity program, awareness, beneficialness, calculation, calm,
   calmness, canniness, cardinal virtues, care, careful consideration,
   carefulness, caution, cautiousness, chariness, charity,
   circumspection, circumspectness, common sense, conservatism,
   consideration, constraint, contemplation, continence, control,
   convenience, cool, cool judgment, custodianship, custody, decency,
   deliberate stages, deliberateness, deliberation, desirability,
   discreetness, discretion, discrimination, dispassion, eagle eye,
   economic planning, economicalness, economy, economy of means,
   envisagement, envisionment, evenness, expedience, expediency,
   faith, false economy, farseeingness, farsightedness, feasibility,
   fitness, fittingness, forecast, foreglance, foregleam, foreglimpse,
   forehandedness, foreseeing, foresight, foresightedness,
   forethought, fortitude, frugality, frugalness, fruitfulness,
   gentleness, gingerliness, golden mean, good judgment,
   good management, guard, guardedness, guardianship, happy medium,
   hedge, hedging, heed, heedfulness, hesitation, hope, husbandry,
   impartiality, insight, invigilation, judgement, judgment,
   judiciousness, juste-milieu, justice, keenness, lenity,
   longsightedness, looking ahead, lookout, love, management,
   meden agan, middle way, mildness, mindfulness, moderateness,
   moderation, moderationism, monitoring, natural virtues, neutrality,
   nonviolence, nothing in excess, observance, opportuneness,
   pacifism, parsimoniousness, parsimony, pawkiness, peeled eye,
   penetration, percentage, percipience, perspicacity, planning,
   policy, politicness, polity, precaution, prediction, preparation,
   preparedness, prepublication, presence of mind, preview, prevision,
   prior consultation, proctoring, profit, profitability, propriety,
   prospect, prospection, providence, provision,
   prudential administration, prudentialism, prudentialness, qui vive,
   readiness, reflection, reflectiveness, regardfulness, repose,
   restraint, rightness, safeness, safety first, sagaciousness,
   sagacity, sageness, sapience, seasonableness, seemliness,
   self-abnegation, self-control, self-denial, self-restraint,
   serenity, sharp eye, shrewdness, slowness to act, sobriety,
   solicitude, sound judgment, soundness of judgment, sparingness,
   stability, steadiness, stewardship, suitability,
   supernatural virtues, surveillance, tact, temperance,
   temperateness, tentativeness, theological virtues, thoroughness,
   thoughtfulness, thrift, thriftiness, tight purse strings,
   timeliness, tranquillity, uncommunicativeness, unexcessiveness,
   unextravagance, unextremeness, unprecipitateness, unwastefulness,
   usefulness, via media, vigil, vigilance, wariness, watch,
   watch and ward, watchful eye, watchfulness, watching, weather eye,
   weighing, wisdom, wit, worthwhileness