Alma Mater (n.)

late 14c., Latin, literally "nurturing mother," a title given by Romans to certain goddesses, especially Ceres and Cybele, from alma, fem. of almus "nourishing," from alere "to nourish, rear, support, maintain" (from PIE root *al- (2) "to grow, nourish") + māter "mother" (see mother (n.1)). In sense of "one's university or school," attested from 1710.

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Definitions of Alma Mater from WordNet

alma mater (n.)
your alma mater is a school you graduated from;