tremendous

Synonyms: amazing appalling astounding awesome awful blimp colossal cracking deafening dreadful enormous excellent exceptional extraordinary fabulous fantastic fearful formidable frightful gargantuan gigantic great great big humongous immense incredible jumbo large mammoth marvelous massive mondo monstrous monumental prodigious stupendous super terrible terrific titanic towering vast whale whopper whopping wonderful

Antonyms: insignificant little small tiny underwhelming unimportant