Real Dictionary

Oxbridge
proper noun: Oxbridge is used to refer to the British universities of Oxford and Cambridge together.

Oxbridge in American English
of or relating to Oxbridge
Oxford and Cambridge universities thought of as forming a single entity in terms of their similar organization, traditions, and prestige
adjective: of, pertaining to, or characteristic of Oxford and Cambridge, or of upper-class, intellectual traditions or manners associated with these universities
noun: Oxford or Cambridge University, or both, esp. in contrast with the other universities of England

Oxbridge in British English
noun: the British universities of Oxford and Cambridge, esp considered as ancient and prestigious academic institutions, bastions of privilege and superiority, etc