There are about a million ways to define hyperbole, but I'm not one to exaggerate for comical, ironic or dramatic effect. I would jump off a cliff before I'd ever use hyperbole in a definition.
The preceding message helps to define what hyperbole is and why a writer might choose to use it. The term is used for a deliberate exaggeration used for dramatic or comic effect in literature. While there may be many examples, using the figure "one million" is a deliberate exaggeration used as shorthand for some significantly high number. The same holds true for the extreme threat of jumping off a cliff. By using dramatic wording, the writer communicates an unspoken level of devotion or passion.
The use of hyperbole as a figure of speech hinges on deliberate exaggeration for a desired effect. If the statement is objectively true, there is no hyperbole. One might say, "The Sears tower is the tallest building in all of Chicago." without any sense of exaggeration or irony.
Another writer might say, "Our new school is large enough to have its own zip code." Obviously few buildings would actually meet this standard, so the exaggeration is for comic or dramatic effect.
There are entire industries built around the power of hyperbole. Advertising agencies routinely use it to build up their client's products and services in the consumers' minds. A new toothpaste, automobile or electronic gadget must be the healthiest, fastest or coolest thing in town.
Many consumers have grown accustomed to such fantastic or hyperbolic claims. Their common mantra is "Don't believe the hype." The word hype is actually derived from the word hyperbole.
The movie industry also depends heavily on the power of hyperbole. Whenever a new motion picture or television program is released, the studio's promotional department will use selected quotes to hype their products, with statements like "The leading man gives the performance of a lifetime!" It really doesn't matter if the actor also gave "the performance of a lifetime" three times the previous year. Without hyperbole, advertisers, storytellers and publicists would probably be looking for other lines of work.