ma·zae·di·um (mə-zē'dē-əm) n.
pl.ma·zae·di·a (-dē-ə) A fruiting body of some lichens in which the spores lie freely in a powdery mass that is enclosed in a peridium.
[New Latin : Greek maza, lump; see mag- in Indo-European roots + Latin aedēs, house.]