An oxymoron is a figure of speech in which two terms that are polar opposites are used together for rhetorical effect, or for the purpose of criticizing a self-contradiction like "pro-life Democrat." Political oxymorons include:
- liberal logic
- government service
- gay charity (the homosexual ideology is entirely selfish)
- evolutionary science
- government intelligence - often used by liberals to smear the Armed Forces
- illegal law - a law that violates the Constitution, for example.
- chicken hawk - a politician who advocates war but personally avoided being drafted into military service.
- salutary neglect - one of the Best New Conservative Terms
- utilitarian justice - can't be both, because justice is individual in nature
- graffiti artist
- liberal Christian - Liberal values are in direct contradiction to the teachings of Christianity (Abortion, Homosexuality etc), but some Christian denominations are able to reconcile these differences (the Moravians, for instance)
- conservative professor - the process of obtaining a PhD and professorship is so politicized that liberals simply exclude conservatives
- good law
- mathematical physics -- the Encyclopedia Britannica defines it as the "[b]ranch of mathematical analysis that emphasizes tools and techniques of particular use to physicists and engineers."
In the past, rhetoric and elocution were standard school subjects and students were taught long lists of technical names of figures of speech and their meaning. Oxymoron was one of these, along with simile, metaphor, metonymy, etc. True oxymoron is relatively rare; one well-known example occurs in Tennyson's Idylls of the King:
- And faith unfaithful kept him falsely true.
- Good night, good night! parting is such sweet sorrow.
Arthur Koestler's book title, Darkness at Noon, is another example.
Since the word oxymoron is derived from the Greek roots oxy, sharp, and moron, dull, it literally means "sharp-dull" and is thus itself an example of an oxymoron.
There is also a punlike form of humor which consists of observing or claiming that certain phrases are oxymorons. While not new, It was popularized by Warren Blumenfeld's 1986 book, Jumbo Shrimp & Other Almost Perfect Oxymorons: Contradictory Expressions That Make Absolute Sense. In literal fact, what is being pointed out is an amusing contradiction.
Originally it played on the fact that many listeners remembered they been taught what an oxymoron was in school, but could not remember what it was. The context would have been something like this:
Humorist: "Jumbo shrimp?" That's an oxymoron.
Mark: [Realizes he should know the word... his ten-grade English teacher drilled him on it... but can't quite, and is forced to ask]: A what?
Humorist: An oxymoron, a contradiction in terms.
Mark: (Thinks about it, realizes that although "Jumbo shrimp" is a real expression, "shrimp" means small and "Jumbo" means large, and rolls on the ground laughing helplessly).
The device has now become so common that the word oxymoron has come to mean this form of humor, which is entirely unrelated to the original meaning of the word. It is often employed to make a political point. It rarely reveals any actual meaning; "Military intelligence is an oxymoron" does not actually point out anything intrinsic in military structure or thinking; it merely puns on the meaning of the phrase "military intelligence" and is just a tricky way of delivering an insult.
Examples of the modern, joking usage:
- Heroic villain - Since villains are bad, calling one heroic is an oxymoron.
- Friendly vandal - A flaw similar to the one above.
Examples of modern, serious usage:
- Jumbo shrimp
- Real nightmare
- same difference
- expect the unexpected
- classic rock
- important game
- The theory of evolution is pseudoscience 
- For example, the Ising model can be used to explain the existence of the Curie point, the temperature above which ferromagnetic materials lose magnetic properties.
- Lancelot and Elaine, Tennyson, Idylls of the King
- Shakespeare, Romeo and Juliet, Act II, Scene 2