The Collaborative International Dictionary of English v.0.48:

Favorable \Fa"vor*a*ble\ (f[=a]"v[~e]r*[.a]*b'l), a. [Written
   also favourable.] [F. favorable, L. favorabilis favored,
   popular, pleasing, fr. favor. See Favor, n.]
   1. Full of favor; favoring; manifesting partiality; kind;
      propitious; friendly.
      [1913 Webster]

            Lend favorable ears to our request.   --Shak.
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            Lord, thou hast been favorable unto thy land. --Ps.
                                                  lxxxv. 1.
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   2. Conducive; contributing; tending to promote or facilitate;
      advantageous; convenient.
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            A place very favorable for the making levies of men.
                                                  --Clarendon.
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            The temper of the climate, favorable to generation,
            health, and long life.                --Sir W.
                                                  Temple.
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   3. Beautiful; well-favored. [Obs.] --Spenser. --
      Fa"vora*ble*ness, n. -- Fa"vor*a*bly, adv.
      [1913 Webster]

            The favorableness of the present times to all
            exertions in the cause of liberty.    --Burke.
      [1913 Webster]

WordNet (r) 3.0 (2006):

favorable
    adj 1: encouraging or approving or pleasing; "a favorable
           reply"; "he received a favorable rating"; "listened with
           a favorable ear"; "made a favorable impression" [syn:
           favorable, favourable] [ant: unfavorable,
           unfavourable]
    2: (of winds or weather) tending to promote or facilitate; "the
       days were fair and the winds were favorable" [syn:
       favorable, favourable] [ant: unfavorable,
       unfavourable]
    3: presaging or likely to bring good luck; "a favorable time to
       ask for a raise"; "lucky stars"; "a prosperous moment to make
       a decision" [syn: golden, favorable, favourable,
       lucky, prosperous]
    4: inclined to help or support; not antagonistic or hostile; "a
       government friendly to our interests"; "an amicable
       agreement" [syn: friendly, favorable, well-disposed]
    5: occurring at a convenient or suitable time; "an opportune
       time to receive guests" [syn: favorable, favourable]

Moby Thesaurus II by Grady Ward, 1.0:

200 Moby Thesaurus words for "favorable":
   accommodating, accommodative, accordant, acquiescent, advantageous,
   advisable, advocating, affirmative, agreeable, agreeing,
   alacritous, amenable, amiable, amicable, approbatory, appropriate,
   approving, ardent, assenting, auspicious, backing, becoming,
   befitting, beneficent, beneficial, benevolent, benign, benignant,
   bon, bonny, brave, braw, bright, bright with promise, brotherly,
   bueno, capital, cheering, cogent, commendable, commendatory,
   compliable, compliant, complimentary, congenial, congruous,
   consentient, consenting, content, convenient, cooperative, decent,
   desirable, dexter, disposed, docile, eager, elegant, encouraging,
   endorsing, enthusiastic, estimable, excellent, expedient, fain,
   fair, famous, favorably disposed, favorably inclined, favoring,
   feasible, felicitous, fine, fit, fitten, fitting, fortunate,
   forward, fraternal, friendlike, friendly, fructuous,
   full of promise, game, golden, good, goodly, grand, grateful,
   gratifying, happy, harmonious, healthful, healthy, helpful,
   helping, in the mind, in the mood, inclined, inspiring,
   inspiriting, kind, kindly, kindly-disposed, laudable, laudatory,
   likely, looking up, lucky, meet, minded, neighborlike, neighborly,
   nice, noble, nothing loath, of good omen, of happy portent,
   of promise, opportune, peaceable, permissive, pleasant, pleasing,
   pleasurable, pleasureful, pliant, politic, positive, praiseful,
   predisposed, pregnant of good, pro, profitable, promising, prompt,
   prone, proper, propitious, prosperous, providential, quick,
   ratifying, ready, ready and willing, reassuring, receptive,
   recommendable, recommendatory, regal, responsive, right, ripe,
   royal, salutary, sanctioning, seasonable, seemly, simpatico,
   sisterly, skillful, sociable, sortable, sound, splendid,
   submissive, suitable, supporting, supportive, sympathetic,
   sympathique, timely, to be desired, toward, tractable, ungrudging,
   unhostile, unloath, unrefusing, unreluctant, useful, valid,
   very good, virtuous, welcome, well-affected, well-disposed,
   well-inclined, well-intentioned, well-meaning, well-meant,
   well-timed, white, wholesome, willed, willing, willinghearted,
   wise, worthwhile, zealous