noun
An organization for graduates of a school, often involved in networking, reunions, and supporting the school.
彼は大学の校友会の役員をしている。
He serves as an officer of his university's alumni association.
同窓会 usually refers to a class reunion or a gathering of graduates, while 校友会 is the formal organization itself.
Compound of 校友 (kōyū, 'schoolmate' or 'alumnus') and 会 (kai, 'association').