The Collaborative International Dictionary of English v.0.48:

Alumna \A*lum"na\, n. fem.; pl. Alumn[ae] . [L. See
   Alumnus.]
   A female pupil; especially, a graduate of a school or
   college.
   [1913 Webster]

WordNet (r) 3.0 (2006):

alumna
    n 1: a person who has received a degree from a school (high
         school or college or university) [syn: alumnus, alumna,
         alum, graduate, grad]