Litotes is an understatement for rhetorical effect.
Here are links to our lists for AP English literary terms: Chiasmus, Litotes, Metaphor, Simile, Zeugma
"Linton's looks and movements were very languid, and his form extremely slight; but there was a grace in his manner that mitigated these defects, and rendered him not unpleasing."
--Wuthering Heights, Emily Bronte
having a chance of occurring too low to inspire belief
"Not improbably, it was to this latter class of men that Mr. Dimmesdale, by many of his traits of character, naturally belonged."
--The Scarlet Letter, Nathaniel Hawthorne
"We are accustomed to look upon the shackled form of a conquered monster, but there—there you could look at a thing monstrous and free. It was unearthly, and the men were—No, they were not inhuman. Well, you know, that was the worst of it—this suspicion of their not being inhuman."
--Heart of Darkness, Joseph Conrad
"Fanny, with all her faults of ignorance and timidity, was fixed at Mansfield Park, and learning to transfer in its favour much of her attachment to her former home, grew up there not unhappily among her cousins."
--Mansfield Park, Jane Austen
"Not uninspired appear their simplest ways;
Their voices mount symbolical of praise--
To mix with hymns that Spirits make and hear;
And to fallen man their innocence is dear."
--"Humanity," William Wordsworth
“Have you not done tormenting me with your accursed time! It's abominable! When! When! One day, is that not enough for you, one day he went dumb, one day I went blind, one day we'll go deaf, one day we were born, one day we shall die, the same day, the same second, is that not enough for you? They give birth astride of a grave, the light gleams an instant, then it's night once more.”
--Waiting for Godot, Samuel Beckett
This is an example of litotes because it purposefully underestimates the span of a human life, while at the same time questioning if this "one day" is enough or, indeed, too much.
"O, reason not the need! Our basest beggars
Are in the poorest thing superfluous.
Allow not nature more than nature needs,
Man’s life’s as cheap as beast’s."
--King Lear, William Shakespeare
This quote is a litotes because it justifies having something (in this case Lear's attendants) by saying that no one "needs" anything, that even the poorest have something, and in fact they have too much, that is, too much poverty.