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Meaning of ostium

os•ti•um

Pronunciation: (os'tē-um), [key]
— pl. -ti•a
  1. a small opening or orifice, as at the end of the oviduct.
  2. one of the tiny holes in the body of a sponge.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.