| Noun | 1. | genus Rhea - type genus of the Rheidae; large tall flightless South American birds similar to but smaller than ostriches bird genus - a genus of birds family Rheidae, Rheidae - a family of birds coextensive with the order Rheiformes Rhea americana, rhea - larger of two tall fast-running flightless birds similar to ostriches but three-toed; found from Brazil to Patagonia |