polygonaceous,a.Bot.|pəˌlɪgəʊˈneɪʃəs| [f.mod.L. Polygonāceæ (f. Polygonum) + -ous: see -aceous.] Belonging to the family Polygonaceæ, of which the typical genus is Polygonum. 1874Cooke Fungi 41 The species attack the flowers and anthers of composite and polygonaceous plants.