Hiatus

(hi-af -tus). A space or opening. Also, the vulva. H. aortic us. See Aortic Opening. H. of Fallopius, the shallow groove on the petrous portion of the temporal bone. H. sacral is, a slit-like opening on the posterior surface of the sacrum. It is continuous above with the spinal canal. H. semilunar is, a crescentic furrow upon the outer wall of the middle meatus of the nose.