Source : Webster's Revised Unabridged Dictionary (1913)

AEcidium \[AE]*cid"i*um\, n.; pl. {[AE]cidia}. [NL., dim. of Gr.
   ? injury.] (Bot.)
   A form of fruit in the cycle of development of the Rusts or
   Brands, an order of fungi, formerly considered independent
   plants.