MeconidiumMec`o*nid"i*um\, n. [NL., dim. of Gr. ? a poppy. So called in allusion to the shape of the seed capsules of the poppy.] (Zo["o]l.) A kind of gonophore produced by hydroids of the genus Gonothyr[ae]a. It has tentacles, and otherwise resembles a free medusa, but remains attached by a pedicel.