[syn: frightful, terrible, awful, tremendous]
The Collaborative International Dictionary of English v.0.48:
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.
   [1913 Webster]
         A tremendous mischief was a foot.        --Motley.
   [1913 Webster]
   Syn: Terrible; dreadful; frightful; terrific; horrible;
        awful.
        [1913 Webster] -- Tre*men"dous*ly, adv. --
        Tre*men"dous*ness, n.
        [1913 Webster]
WordNet (r) 3.0 (2006):
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,
           tremendous]
    2: extraordinarily good or great ; 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, grand,
       howling(a), marvelous, marvellous, rattling(a),
       terrific, tremendous, wonderful, wondrous]
    3: extreme in degree or extent or amount or impact; "in a
       frightful hurry"; "spent a frightful amount of money" [syn:
       frightful, terrible, awful, tremendous]
Moby Thesaurus II by Grady Ward, 1.0:
104 Moby Thesaurus words for "tremendous":
   Atlantean, Brobdingnagian, Cyclopean, Gargantuan, Herculean,
   Homeric, abysmal, amazing, amplitudinous, appalling, astounding,
   astronomic, astronomical, awe-inspiring, awesome, awful, boundless,
   bulky, colossal, cosmic, cracking, dire, direful, divine, dread,
   dreaded, dreadful, elephantine, enormous, epic, exquisite,
   extensive, fantastic, fell, flabbergasting, formidable, frightful,
   galactic, ghastly, ghoulish, giant, giantlike, gigantic,
   gilt-edged, glorious, golden, grim, grisly, gruesome, heavenly,
   heroic, hideous, horrendous, horrible, horrid, horrific,
   horrifying, huge, immeasurable, immense, infinite, jumbo,
   king-size, large, macabre, magnificent, mammoth, marvelous,
   massive, massy, mighty, monster, monstrous, monumental, morbid,
   mortal, mountainous, outsize, overgrown, prodigious, profound,
   redoubtable, schrecklich, sensational, shocking, sizable, spacious,
   splendid, splendiferous, sterling, stupendous, super, superb,
   supereminent, superexcellent, superfine, terrible, terrific,
   titanic, towering, vast, voluminous, weighty, wonderful