Which term describes a figure of speech where what is said is the opposite of what is meant?

Verbal irony is a figure of speech in which a speaker says one thing but means another, often conveying a meaning that is opposite to the literal interpretation of the words used. This can be employed for various effects, such as humor, sarcasm, or emphasis on a particular point. For example, if someone looks out at a rainy day and says, "What a lovely day!" they are using verbal irony to imply the opposite of the literal statement.

In contrast, the other terms refer to different literary devices: a metaphor expresses an idea by stating that one thing is another, a simile compares two different things using "like" or "as," and alliteration involves the repetition of consonant sounds at the beginning of nearby words. Each of these serves distinct purposes in language but does not convey the idea of saying one thing while meaning another, which makes verbal irony the correct choice.