Also called a Serial or Harvard Comma, it is a punctuation used immediately before a grammatical conjunction. Ezra Koenig, Rostam Batmanglij, Chris Tomson, and Chris Baio (Oxford Commas are used between the names.)

But the preppy indie band Vampire Weekend also uses the term to refer to a white, preppy guy from Oxford, as "comma" has also been used as slang for an obnoxious white person.

an oxford comma is a small curly-que of a turd squeezed out onto your dick when you are fucking a girl doggy-style.