An oxymoron (plural oxymorons or, more rarely, oxymora) is a figure of speech that combines two normally contradictory terms. Oxymoron is a loanword from Greek oxy ("sharp" or "pointed") and moros ("dull"). Thus the word oxymoron is itself an oxymoron.
Oxymorons are a proper subset of the expressions called contradictions in terms. What distinguishes oxymorons from other paradoxes and contradictions is that they are used intentionally, for rhetorical effect, and the contradiction is only apparent, as the combination of terms provides a novel expression of some concept, such as "cruel to be kind" or "team of mavericks".