1) Agt 2) Awesome 3) Big 4) Brobdingnagian 5) Enormous 6) Excellent 7) Extraordinary 8) Great 9) Huge 10) Immeasurable 11) Irresistible 12) Large 13) Marvellous 14) Marvelous 15) Outstanding 16) Overwhelming 17) Rattling 18) Super 19) Unforgettable 20) Wonderful 21) Wondrous 1) Enormous 2) Extraordinarily good or great 3) Extraordinary or excellent 4) Large 5) Terrific 
• (a.) 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.
[Adjective] Very big, enormous.
extreme in degree or extent or amount or impact