coruler

noun

co·​rul·​er (ˌ)kō-ˈrü-lər 

variants or co-ruler

plural corulers or co-rulers

: someone who rules with another

… they deposed him and put in his place his son, Stephen Dushan, who had until then served as coruler.

—Cyril E. Black

Such was the royal ardor that it took guilt over the death of his wife and co-ruler Queen Mary to end the affair.

—Martin Rubin

Word History

First Known Use

1677, in the meaning defined above