1799, from under + statement.

See litotes and meiosis under tropes.

a statement that is restrained in ironic contrast to what might have been said (understated) exhibiting restrained good taste; "the room is pleasant and understated" Understa [..]

The opposite of hyperbole, understatement is used to make something appear smaller or less important than it really is. It can be used to entertain or to reduce the importance of the truth. See [..]

A figure of speech in which a writer or speaker says less than what he or she means; the opposite of exaggeration. The last line of Frost's "Birches" illustrates this literary device: "One could do worse than be a swinger of birches."

language that makes it point by self-consciously downplaying its real emphasis, as in "Final exams aren’t exactly a walk in the park"; litotes is one form of understatement. See also [..]

 – saying less than what is meant

An "understatement" is defined as “the excess of the tax required to be shown on the return over the tax actually shown on the return. An understatement of income tax is "substantial&qu [..]

(n) a statement that is restrained in ironic contrast to what might have been said

saying that something is smaller or less important than it actually is.