1PGO to rule a nation or group of nations as their king, queen, or emperor :
George VI reigned from 1936 to 1952.
George VI reigned from 1936 to 1952.2 literary if a feeling or quality reigns, it exists strongly for a period of time :
3 the most recent winner of a competition :
Can he defeat the reigning Wimbledon champion?
reigning champion
DS
Can he defeat the reigning Wimbledon champion?4 if someone or something reigns supreme, they are the most important part of a situation or time :
It was a time when romance reigned supreme.
reign supreme
It was a time when romance reigned supreme.