reg·nant 
(rĕgnənt)
(rĕgnənt)adj.
1. Reigning; ruling: a queen regnant.
2. Predominant.
3. Widespread; prevalent.
[Probably from Middle English, a sovereign, from Old French, from Latin rēgnāns, rēgnant-, present participle of rēgnāre, to reign, from rēgnum, reign; see REIGN.]