1. [n]  a resident of Oxford
2. [adj]  of or pertaining to or characteristic of the city of Oxford, England, or its inhabitants; "his Oxonian neighbors"; "Oxonian bookstores"
3. [adj]  of or pertaining to or characteristic of Oxford University; "Oxonian education"

OXONIAN is a 7 letter word that starts with O.

1. \Ox*o"ni*an\, a.
   Of or relating to the city or the university of Oxford,
   England. --Macaulay.
   
   

2. \Ox*o"ni*an\, n.
   A student or graduate of Oxford University, in England.