The Collaborative International Dictionary of English v.0.48:

Alma Mater \Al"ma Ma"ter\ [L., fostering mother.]
   A college or seminary where one is educated.
   [1913 Webster]

WordNet (r) 3.0 (2006):

alma mater
    n 1: your alma mater is a school you graduated from

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "alma mater":
   academe, academia, college, college of engineering,
   community college, degree-granting institution, four-year college,
   graduate school, institute of technology, ivied halls,
   journalism school, junior college, law school, medical school,
   multiversity, normal, normal school, postgraduate school,
   school of communications, school of education, two-year college,
   university, university college, varsity