pileus

Pi"le*us, n.; pl. Pilei. Etym: [L., a felt cap.] 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. (Zoöl.) Defn: The top of the head of a bird, from the bill to the nape.

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