1. enormous, immense, prodigious, herculean, cyclopean, titanic. Gigantic, colossal, mammoth, monstrous are used of whatever is physically or metaphorically of great magnitude. Gigantic refers to the size of a giant, or to size or scope befitting a giant: a gigantic stalk of corn. Colossal refers to the size of a colossus, to anything huge or vast as befitting a hero or god: a colossal victory. Mammoth refers to the size of the animal of that name and is used especially of anything large and heavy: a mammoth battleship. Monstrous means strikingly unusual or out of the normal in some way, as in size: a monstrous blunder.