alumni association; old boys' association
Refers to a group or gathering of former members (graduates, ex-employees, etc.), often of a school or company. The term ＯＢ (old boy) is borrowed from English and commonly used in Japanese for male alumni; the female equivalent is ＯＧ (old girl).
See also: ＯＢ
Next month, the university's alumni association will hold a meeting.
He serves as the secretary of the old boys' association.
Kana spelling of the ＯＢ part; sometimes used in informal writing or when the Latin letters are avoided.
Compound of ＯＢ (from English 'old boy', meaning a male former member) and 会 (association, meeting).