What do you call a word that is used overtly to mean something besides its actual meaning?

Solution 1:

This is an example of the rhetorical device of hyperbole:

extravagant exaggeration (such as "mile-high ice-cream cones")

From Merriam-Webster

The word is from Greek and means excess. It has come to mean a figure of speech that uses extreme exaggeration for emphasis or to make a point.

The word originally meant "to throw over":

"obvious exaggeration in rhetoric," early 15c., from Latin hyperbole, from Greek hyperbole "exaggeration, extravagance," literally "a throwing beyond," from hyper- "beyond" (see hyper-) + bole "a throwing, a casting, the stroke of a missile, bolt, beam," from bol-, nominative stem of ballein "to throw" (from PIE root *gwele- "to throw, reach"). Rhetorical sense is found in Aristotle and Isocrates. Greek had a verb, hyperballein, "to throw over or beyond."

From the Online Etymology Dictionary