| Noun | 1. | family Rheidae - a family of birds coextensive with the order Rheiformes bird family - a family of warm-blooded egg-laying vertebrates characterized by feathers and forelimbs modified as wings order Rheiformes, Rheiformes - a ratite bird order: birds intermediate in characteristics between ostriches and emus: recent and extinct rheas genus Rhea - type genus of the Rheidae; large tall flightless South American birds similar to but smaller than ostriches genus Pterocnemia, Pterocnemia - a genus of birds of the family Rheidae |