1. A ruler: In the book about the 15th century, a governing person was termed a regent.
2. One who governs as a substitute for a monarch: A regent was invested with ruling power because the king had died and the young prince was only two years old!
3. A member of the governing board of a university or college: Jack found out that a regent was part of the governing body in Scotland, in the U.S.A., and in Canada.