ba·sid·i·um 
(bə-sĭdē-əm)
(bə-sĭdē-əm)n. pl. ba·sid·i·a (-ē-ə)
A small, specialized club-shaped structure typically bearing four basidiospores at the tips of minute projections. The basidium is unique to basidiomycetes and distinguishes them from other kinds of fungi.
[BAS(I)- + Latin -idium, diminutive suff. (from Greek -idion).]
ba·sidi·al adj.