eu·ba·sid·ii \-dēˌī\noun plural Usage: capitalized Etymology: New Latin, from eu- + -basidii (from basidium) in some classifications: a subclass of fungi including all those basidiomycetes in which the basidium arises directly from vegetative cells of the diploid mycelium (as the puffballs, jelly fungi, pore fungi, and related forms) — compare hemibasidii, heterobasidiomycetes