Grad and Old boy

Grad noun - A person who has received a degree from a school (high school or college or university).

Old boy and grad are semantically related. In some cases you can replace phrase "Old boy" with "Grad", this terms are similar.

Old boy noun - A former male pupil of a school.

Grad and old boy are semantically related. Sometimes you can use "Grad" instead a noun phrase "Old boy".