Definition of pileus
plural pilei
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\ˈpī-lē-ˌī\
1
[Latin]
: a pointed or close-fitting cap worn by ancient Romans
2
: the convex, concave, or flattened spore-bearing structure of some basidiomycetes that is attached superiorly to the stem and typically is expanded with gills or pores on the underside — called also
cap
