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1. Extraordinarily large in size, extent, amount, power or degree
   "tremendous sweeping plains"; "a tremendous fact in human experience; that a whole civilization should be dependent on technology"; "a plane took off with a tremendous noise";
   - enormous, ginormous [Brit, informal]
    
2. Extraordinarily good or great; used especially as an intensifier
   "a tremendous achievement";
   - fantastic, grand, howling [informal], marvelous [US], marvellous [Brit, Cdn], rattling [informal], terrific, wonderful, wondrous, phenomenal, epic [slang], magnificent, heavenly [informal]
    
3. Extreme in degree, extent, amount or impact
   "in a tremendous hurry";
   - frightful, terrible, awful

See also: big, extraordinary, large

Encyclopedia: Tremendous