Sporidium \Spo*rid"i*um\ (sp[-o]*r[i^]d"[i^]*[u^]m), n.; pl. {Sporidia} (-[.a]). [NL. See {Spore}.] (Bot.) (a) A secondary spore, or a filament produced from a spore, in certain kinds of minute fungi. (b) A spore. [1913 Webster]