Oxymoron

An oxymoron (plural oxymorons or oxymora) is "a figure of speech that juxtaposes concepts with opposite meanings" inside a word or phrase that contradicts itself: "bittersweet," "cruel kindness," "jumbo shrimp." The etymology is itself one, Greek oksús, "sharp, keen, pointed," against mōros, "dull, stupid, foolish." Compound words hide them too, preposterous ("with the hinder part before") and sophomore ("wise-foolish") among them. Literature's showcase is Romeo in Romeo and Juliet stringing thirteen in a row: "O brawling love! O loving hate!" and "Feather of lead, bright smoke, cold fire, sick health!"

The article's distinctions keep the device honest: narrowly, oxymorons are intentional, recognized by speaker and listener, and the figure works "to communicate and reveal a paradox" rather than being one. In a novel the controlled collision is the aim, a phrase saying two incompatible true things at once. It belongs to the figurative family of metaphor and hyperbole; an accidental one is usually a sign the sentence needs another pass.