Pileus
Pronunciation : Pi"le*us
Part of Speech : n.;
Etymology : [L., a felt cap.]
Definition : 1. (Rom. Antiq.)
Defn: A kind of skull cap of felt.
2. (Bot.)
Defn: The expanded upper portion of many of the fungi. See Mushroom.
3. (Zo?l.)
Defn: The top of the head of a bird, from the bill to the nape.
pl. Pilei.
Source : Webster's Unabridged Dictionary, 1913