Overstatement or exaggeration for the sake of emphasis, as when the little boy says “Hey Dad there's thousands of cats in our yard!” As literary devices, hyperbole, and its opposite understatement (litotes), are much used in comedy and satire.
Editors. "Hyperbole". The Literary Encyclopedia. First published 01 November 2001
[http://www.litencyc.com/php/stopics.php?rec=true&UID=527, accessed 01 February 2015.]