OxfordianPronunciation: /ɒksˈfɔːdɪən/Definition of Oxfordian adjective 1 Geology relating to or denoting an age in the Upper Jurassic period, lasting from about 157 to 155 million years ago. Also called Corallian. 2relating to or denoting the theory that Edward de Vere (1550–1604), Earl of Oxford, wrote the plays attributed to Shakespeare. noun 1 (the Oxfordian) Geology the Oxfordian age or the system of rocks (chiefly coral-derived limestones) deposited during it. 2a supporter of the Oxfordian theory.