Pronunciation: (per'u-stōm"), [key]
1. Bot.the one or two circles of small, pointed, toothlike appendages around the orifice of a capsule or urn of mosses, appearing when the lid is removed.
2. Zool.any of various structures or sets of parts that surround or form the walls of a mouth or mouthlike opening.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.