Source : Webster's Revised Unabridged Dictionary (1913)

Tremendous \Tre*men"dous\, a. [L. tremendus that is to be
   trembled at, fearful, fr. tremere to tremble. See {Tremble}.]
   Fitted to excite fear or terror; such as may astonish or
   terrify by its magnitude, force, or violence; terrible;
   dreadful; as, a tremendous wind; a tremendous shower; a
   tremendous shock or fall.

         A tremendous mischief was a foot.        --Motley.

   Syn: Terrible; dreadful; frightful; terrific; horrible;
        awful. -- {Tre*men"dous*ly}, adv. --
        {Tre*men"dous*ness}, n.

Source : WordNet®

tremendous
     adj 1: extraordinarily large in size or extent or amount or power
            or degree; "an enormous boulder"; "enormous expenses";
            "tremendous sweeping plains"; "a tremendous fact in
            human experience; that a whole civilization should be
            dependent on technology"- Walter Lippman; "a plane
            took off with a tremendous noise" [syn: {enormous}]
     2: 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},
         {marvellous}, {rattling(a)}, {terrific}, {wonderful}, {wondrous}]