Longman Dictionary of Contemporary English - old boy

~ n 1 BrE a man who used to be a student at a particular school  (an old boys' reunion) 2 the old-boy network the system by which men from rich families, men who went to the same school, belong to the same club etc, use their influence to help each other 3 BrE spoken an old man  (the old boy from down the road) 4 BrE old-fashioned a way of addressing a male friend  (How are you, old boy?)  (- compare old girl)