Definition of old girl noun from the Oxford Advanced Learner's Dictionary

  1. 1old girl
    BrE
     
    ; NAmE
     
    (British English) a woman who used to be a student at a particular school, usually a private one There’s going to be an old girls’ reunion next month.
  2. 2old girl
    BrE
     
    ; NAmE
     
    (informal, especially British English) an old woman The old girl next door has died.