: any of various bodily cavities especially when serving as or resembling an entrance to some other cavity or space: such as
a : the central cavity of the bony labyrinth of the inner ear or the parts (such as the saccule and utricle) of the membranous labyrinth that it contains
b : the part of the left ventricle below the aortic orifice
c : the space between the labia minora containing the orifice of the urethra
d : the part of the mouth cavity outside the teeth and gums