obturator

noun

1. An object used to obstruct a hole, such as a fissure of the palate.
2. The membrane vessels, etc. that close the obturator foramen, or thyroid foramen, a large opening or fenestra in the anterior part of the hip bone.
3. A valve closure member (disk, gate, plug, etc.).

   “Obturators, held down by compressed air, close the pipe giving direct access from the h.p. exhaust to the l.p. steam chest, and so prevent compound working; […].”

4. Any device for preventing the escape of gas through the breech mechanism of a breech-loading gun; a gas check.
5. A camera shutter.