noun The cupulate fruiting body borne upon the mycelium of certain fungi commonly parasitic upon specimens of the Compositae, Lamiaceae, Leguminosae, and Ranunculaceae families
noun A member of the form genus Aecidium.
noun ↑ “æcidium” listed in the Oxford English Dictionary, second edition, 1989
noun ↑ listed in the online Merriam-Webster. Retrieved 4 June 2018.