introitus

noun2

1. •
   The entrance to a hollow organ or canal; often specifically the entrance to the vagina.

   • During NA therapy, 49 of the 54 women cleared their introitus of all Enterobacteriaceae. — 1980
2. •
   A piece of music played before a mass; a musical introduction of any sort.

   • Five have an introitus (introduction) that stands outside the isorhythmic scheme;¹⁰⁸ some of these introitus are instrumental rather than vocal […] — 1954