A deliberate exaggeration that no one takes literally, used to emphasize a feeling or a situation.
In Julius Caesar
Why, man, he doth bestride the narrow world / Like a Colossus, and we petty men / Walk under his huge legs and peep about / To find ourselves dishonorable graves
Cassius exaggerates on purpose: the world becomes "narrow" and Caesar a giant with legs spread wide, under whom the others look for a "dishonorable grave." No one takes this literally, but the image shows how small he feels.