What is Alumnus?

Legal Definition
An alumnus (/əˈlʌmnəs/; masculine, plural alumni /əˈlʌmn/) or an alumna (/əˈlʌmnə/; feminine, plural alumnae /əˈlʌmn/) is a former student or pupil of a school, college, or university. Commonly, but not always, the word refers to a graduate of the educational institute in question. An alumnus can also be a former member, employee, contributor, or inmate, as well as a former student.
-- Wikipedia
Legal Definition
A child which one has nursed ; a foster-child. Dig. 40, 2, 14. One educated at a college or seminary is called an "alumnus" thereof.
-- Black's Law Dictionary
Legal Definition
Civil law. A child which one has nursed; a foster child. Dig. 40, 2, 14.
-- Bouviers Law Dictionary