alumnus
alumnus n pl. alumni
A male graduate or former student of a school, college, or university.
Usage Note: Alumnus and alumna both come from Latin and preserve Latin plurals. Alumnus is a masculine noun whose plural is alumni, and alumna is a feminine noun whose plural is alumnae. Coeducational institutions usually use alumni for graduates of both sexes. But those who object to masculine forms in such cases may prefer the phrase alumni and alumnae or the form alumnae/i, which is the choice of many women’s colleges that have begun to admit men. (AHD4)
alum n AMERICAN INFORMAL
someone who was a student at a particular high school, university, or college:
alum of: She and I are alums of the same university. (MEDA)