Source : Webster's Revised Unabridged Dictionary (1913)

Marvelous \Mar"vel*ous\, a. [OE. merveillous, OF. merveillos, F.
   Merveilleux. See {Marvel}, n.] [Written also {marvellous}.]
   1. Exciting wonder or surprise; astonishing; wonderful.

            This is the Lord's doing; it is marvelous in our
            eyes.                                 --Ps. cxiii.
                                                  23.

   2. Partaking of the character of miracle, or supernatural
      power; incredible.

            The marvelous fable includes whatever is
            supernatural, and especially the machines of the
            gods.                                 --Pope.

   {The marvelous}, that which exceeds natural power, or is
      preternatural; that which is wonderful; -- opposed to {the
      probable}.

   Syn: Wonderful; astonishing; surprising; strange; improbable;
        incredible.

   Usage: {Marvelous}, {Wonderful}. We speak of a thing as
          wonderful when it awakens our surprise and admiration;
          as marvelous when it is so much out of the ordinary
          course of things as to seem nearly or quite
          incredible.

Source : WordNet®

marvellous
     adj 1: extraordinarily good; used especially as intensifiers; "a
            fantastic trip to the Orient"; "the film was
            fantastic!"; "a howling success"; "a marvelous
            collection of rare books"; "had a rattling
            conversation about politics"; "a tremendous
            achievement" [syn: {fantastic}, {howling(a)}, {marvelous},
             {rattling(a)}, {terrific}, {tremendous}, {wonderful},
             {wondrous}]
     2: being or having the character of a miracle [syn: {marvelous},
         {miraculous}]
     3: too improbable to admit of belief; "a tall story" [syn: {improbable},
         {marvelous}, {tall(a)}]