A Hyperbole is a term that refers to statements made in a particular work of fiction that are exaggerations of the actual truth of the matter. Often hyperboles are used as evidence in debates, and it can be very difficult to tell if a statement is a hyperbole or not.
A general rule is that if a claim is made that is completely out of league of anything ever shown in said universe (for example, if someone claimed to be a planet buster in a verse where the strongest feats were city busting), it's most likely a hyperbole.
In universes with a wide range of characters on different tiers of power (such as Marvel and DC), this has to be evaluated on an individual character basis, instead of on the verse as a whole.
For example, if someone in One Piece claimed that they could destroy an island, it's reasonable to consider it a possibility, since other people in the verse (ex. Whitebeard) have done comparable things (of course, it still has to be evaluated based on the feats and power-scaling of the actual character).
On the other hand, if someone said Spider-Man could destroy a star, it's unreasonable to think this is true despite the fact that Herald - level characters and above in Marvel have done so, because Spider-Man is established as being on a lower tier than such characters.
Another way of determining weather a statement is a hyperbole or not is to consider the likelihood that a character was misinformed, ignorant, lying, exaggerating, bluffing, mentally unstable, etc. when they made said statement. If there is not any evidence that they were, it can be taken more seriously. Of course, this method isn't as accurate as the feat scaling method above, and should only be relied upon if the first method doesn't give any clear answers.
Notable Examples of hyperbole:
Yu Yu Hakusho characters claiming that they are capable of destroying the planet.
Juggernaut being unstoppable (although against most opponents in general, he might as well be).