1. currently ruling as a monarch
2. currently holding a title or championship
3. most prominent or dominant at the present time

Examples

• The reigning monarch addressed the nation on television.
• She is the reigning world champion in tennis.
• The reigning theory in physics was challenged by new evidence.
• He defeated the reigning champion in straight sets.
• The reigning queen celebrated her golden jubilee.
• That restaurant is the reigning favorite among food critics.
• The reigning champion will defend her title next month.