old boy

old boy noun
plural old boys
old boy
noun
plural old boys
Britannica Dictionary definition of OLD BOY
[count]
1 
chiefly British or Old Boy : a person who went to a respected or well-known private school for boys — compare old girl
2 
chiefly British, informal : an old man

old boy network

usually disapproving also old boys' network
: an informal system in which wealthy men with the same social and educational background help each other