1) A small, oval, bony chamber of the labyrinth. The vestibule contains the utricle and saccule, organs which are part of the balancing apparatus of the ear.

2) Anatomical cavity that connects an organ cavity, organ cavity subdivision or cavity of body part subdivision to the exterior, completely or partially surrounded by organs or organ parts that are lined by epithelium. Examples: preputial cavity, vestibule of vagina.

3) Structures of the inner ear concerned with reception and transduction of stimuli of equilibrium; they include the semicircular canals, the utricle, and the saccule.

4) Major organ of equilibrium which acts as a sensory receptor that detects the position and changes in the position of the head in space.

5) Any of various bodily cavities especially when serving as or resembling an entrance to some other cavity or space: as (a) 1: the central cavity of the bony labyrinth of the ear, 2: the parts of the membranous labyrinth comprising the utricle and the saccule and contained in the cavity of the bony labyrinth (b): the space between the labia minora containing the orifice of the urethra (c): the part of the left ventricle of the heart immediately below the aortic orifice (d): the part of the mouth cavity outside the teeth and gums.