Pride and Prejudice begins with the iconic sentence:
It is a truth universally acknowledged that a single man in possession of a good fortune must be in want of a wife.
However, with the very next sentence (in the following paragraph), we observe a bit of situational irony at play:
However little known the feelings or views of such a man may be on his first entering a neighborhood, this truth is so well fixed in the minds of the surrounding families, that he is considered as the rightful property of some one or other of their daughters.
Situational irony ultimately entails a reversal of expectations. Reading these two sentences together might provide a sense for how this literary device tends to function.
In the book's opening sentence, Austen describes a wealthy gentleman who represents the apex of the society Austen depicts, one divided strictly along lines of class and gender that expects rigid conformity to various social norms. It is a highly sexist and patriarchal society in addition to a classist one, and in all these respects, it could be expected that, when it comes to matters of matrimony, power and agency would rest with the males.
But this is where Austen's clever and ironic wordplay comes into effect, because in the very next paragraph she introduces the contrasting idea that, due the very predictability of this society, these most powerful and esteemed men are instead viewed by "the surrounding families ... as the rightful property of ... their daughters." In this way, the expected power dynamics appear to have been flipped, with the wealthy and influential gentleman losing agency. Chained by the the customs and expectations of the very same society he dominates, he has been reduced to the status of quarry, pursued by the women and their families.