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Vestibule of vulva; vestibule of vagina; the space between the labia minor containing the openings of the vagina and urethra.
A large vestibule in the house led from the kitchen to the garden.
The priest was concerned about damaged windows in the vestibule of the church.
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Yes the word vestibule is a noun. It is a common noun.
When I entered their home, I walked through the vestibule and proceeded upstairs.