Definitions:

1. To hold royal office or rule as a monarch or leader. VERB
   • The queen is still reigning over the country after several decades on the throne.
2. Used figuratively to refer to someone or something that is currently dominating or leading in a particular field or area. VERB
   • He is the reigning champion, having won the tittle fro three consecutive years.

Synonyms:

• commanding
• dominating
• governing
• leading
• presiding
• prevailing
• regnant
• ruling