adjective

of very great size or extent; huge or enormous.

a gigantic concrete tower

huge,enormous,vast,extensive,expansive,broad,wide,very big/large,great,giant,massive,colossal,mammoth,immense,tremendous,mighty,stupendous,monumental,boundless,immeasurable,limitless,infinite,cosmic,epic,prodigious,mountainous,monstrous,titanic,towering,elephantine,king-sized,king-size,gargantuan,Herculean,Brobdingnagian,substantial,mega,monster,whopping,whopping great,thumping,thumping great,humongous,jumbo,hulking,bumper,astronomical,astronomic,whacking,whacking great,ginormous