Struthioniformes strut·hio·ni·formes uncommon noun 1. a ratite bird order: ostriches and related extinct birds; known from the Pleistocene onward Synonymsorder Struthioniformes Related words Broader terms animal order Parts Aves Part of Struthionidae WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.