Definition of os internum in US English:

os internum

noun

rare, historical
  • Originally: †the opening of the cervix into the vagina (obsolete). In later use: the constriction of the cervical canal at the junction with the body of the uterus.

Origin

Mid 18th century; earliest use found in William Smellie (1697–1763), man-midwife. From post-classical Latin os internum from classical Latin ōs + internum, neuter of internus inner.

Pronunciation

os internum

/ˌɒs ɪnˈtəːnəm/