rhetorical device
Definition - Any word or phrase that deviates from the normal literal use of words in order to add beauty, variety, or emphasis to a statement.

1. The common techniques for doing this have been given names, such as hyperbole, hysteron proteron, merism, and metaphor.

Example -
He has tons of money
(i.e. he has lots of money, but it probably doesn't weigh a ton).

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