Hyperbole
HYPER'BOLE, noun hyper'boly. [Gr. excess, to throw beyond, to exceed.]
In rhetoric, a figure of speech which expresses much more or less than the truth, or which represents things much greater or less, better or worse than they really are. An object uncommon in size, either great or small, strikes us with surprise, and this emotion produces a momentary conviction that the object is greater or less than it is in reality. The same effect attends figurative grandeur or littleness; and hence the use of the hyperbole which expresses this momentary conviction. The following are instances of the use of this figure.
He was owner of a piece of ground not larger than a Lacedemonian letter.
If a man can number the dust of the earth, then shall thy seed also be numbered. Genesis 13:16.
Ipse arduus, alta que pulsat Sidera.
He was so gaunt, the case of a flagellet was a mansion for him.