Source : Webster's Revised Unabridged Dictionary (1913)

Reasonable \Rea"son*a*ble\, a. [OE. resonable, F. raisonnable,
   fr. L. rationabilis. See {Reason}, n.]
   1. Having the faculty of reason; endued with reason;
      rational; as, a reasonable being.

   2. Governed by reason; being under influence of reason;
      thinking, speaking or acting rationally, or according to
      the dictates of reason; agreeable to reason; just;
      rational; as, the measure must satisfy all reasonable men.

            By indubitable certainty, I mean that which doth not
            admit of any reasonable cause of doubting. --Bp.
                                                  Wilkins.

            Men have no right to what is not reasonable.
                                                  --Burke.

   3. Not excessive or immoderate; within due limits; proper;
      as, a reasonable demand, amount, price.

            Let . . . all things be thought upon That may, with
            reasonable swiftness, add More feathers to you
            wings.                                --Shak.

   Syn: Rational; just; honest; equitable; fair; suitable;
        moderate; tolerable. See {Rational}.

Reasonable \Rea"son*a*ble\, adv.
   Reasonable; tolerably. [Obs.]

         I have a reasonable good ear in music.   --Shak.

Source : WordNet®

reasonable
     adj 1: showing reason or sound judgment; "a sensible choice"; "a
            sensible person" [syn: {sensible}] [ant: {unreasonable}]
     2: not excessive or extreme; "a fairish income"; "reasonable
        prices" [syn: {fair}, {fairish}]
     3: marked by sound judgment; "sane nuclear policy" [syn: {sane}]