Hyperbole: from the Greek,
huperbole, "excess," oddly unrelated to
hyperbola, which also from Greek,
huperballein, "to throw beyond." A wild exaggeration such as that hoary old chestnut, "I'm so hungry, I could eat a horse." Jack Benny would say that, and after a Benny-esque pause for consideration, admit, "well, a
small horse." The lesson with hyperbole is that it's not very effective all by itself but can be if it's combined with another figure of speech, for example, a pun, "Your mother is so big that when she sits around the house, she really sits around the house," or a paradox, "That river was so wide, it only had one bank," or go to excruciatingly accurate detail as Snoopy does, writing, "His love for her was deeper than the Mariana Trench, which is the deepest spot on earth, over 36 thousand feet."
