Enormous, huge, tremendous, immense; extraordinary in size, extent, force, or degree.
→ Synonyms of prodigious include mammoth, monumental, colossal, gargantuan, elephantine, herculean, and Brobdingnagian.
The last four synonyms are interesting words worthy of brief comment.
Gargantuan (gahr-GAN-choo-in) comes from the name Gargantua, the hero of the famous satirical romance by Franois Rabelais, published in 1532. Gargantua, says the Century Dictionary, is “a giant of inconceivable size, who could drink a river dry. The name is doubtless from Spanish garganta, [throat], gullet.” In modern usage gargantuan sometimes suggests gluttony, as a gargantuan feast, but it is perhaps most often used as a stronger synonym of gigantic or enormous, as a gargantuan house or a gargantuan achievement.
Elephantine (EL-uh-FAN-tin, also EL-uh-FAN-teen or EL-uh-FAN-tyn) may mean pertaining to an elephant, but the word is most commonly used to mean resembling an elephant, and therefore huge, heavy, and awkward. A person may be of elephantine proportions or walk with an elephantine gait. A king-sized bed or an overlarge couch might also be described as elephantine, suitable for an elephant, immense.
The adjective herculean (hur-KYOO-lee-in or HUR-kyoo-LEE-in) comes from the name Hercules, the famous hero of Greek mythology renowned for his great feats of strength and courage. By derivation herculean means worthy or characteristic of the mighty Hercules. A herculean task demands all your strength and stamina; a herculean effort is a mighty, powerful effort. (The word is now usually spelled with a small h.)
The unusual word Brobdingnagian (BRAHB-ding-NAG-ee-in, don’t forget to pronounce the ding) refers to the gigantic inhabitants of the imaginary land of Brobdingnag (BRAHB-ding-nag) in Jonathan Swift’s Gulliver’s Travels, or to anyone or anything equally enormous. Because of its literary flavor and peculiar sound, Brobdingnagian (always spelled with a capital B) is probably best reserved for situations in which you want to achieve a humorous or satirical effect. For example, when your very large, very formidable Aunt Eloise makes her thunderous entrance at your next family reunion, you might greet her by saying, “My dear, you look positively Brobdingnagian this evening!” The antonym of Brobdingnagian is the more familiar word Lilliputian (LIL-i-PYOO-shin), which also comes to us from Swift’s Gulliver’s Travels.
And now back to our keyword. Prodigious comes through the Latin prodigiosus, strange, wonderful, marvelous, from prodigium, an omen, portent, sign. From the same source we have inherited the word prodigy (PRAH-di-jee), a person of marvelous talent or wonderful ability.
Since about 1600, prodigious has been used to mean huge, enormous, of extraordinary size or extent, and also marvelous, wonderful, phenomenal, causing wonder or amazement. In modern usage the context often suggests both senses: a prodigious talent is both enormous and amazing; a prodigious accomplishment is both phenomenal and huge; prodigious energy is both astonishing and tremendous; and a prodigious event or a prodigious undertaking is often both extraordinary and wonderful.
When you think of the word prodigious, consider this: William Shakespeare composed twenty of his plays in only ten years, an output that can only be described as prodigious.