Definition of Oxford comma in English:

Oxford comma

noun

  • A comma used after the penultimate item in a list of three or more items, before ‘and’ or ‘or’ (e.g. an Italian painter, sculptor, and architect).

    Also called serial comma
    • ‘Did you know using the Oxford comma is simply a matter of personal taste?’
    • ‘In the UK, for instance, Oxford University Press goes against general usage by favouring " ize’ word endings (on etymological grounds) and the’Oxford comma’, aka the Harvard or serial comma.’
    • ‘Others insist on the Oxford comma as in ‘counties like Mayo, Sligo, and Galway’ instead of Mayo, Sligo and Galway’.’

Origin

A characteristic of the house style of Oxford University Press.