| Noun | 1. | genus Dioon - small genus of arborescent cycads of Mexico and Central America; sometimes classified in family Cycadaceae gymnosperm genus - a genus of gymnosperms family Zamiaceae, zamia family, Zamiaceae - a family of cycads often included in the family Cycadaceae: zamias dioon - any cycad of the genus Dioon; handsome palmlike cycads with robust crowns of leaves and rugged trunks |