syneisaktism

Etymology
From, from , from +.

Noun

 * 1)  The practice, from early Christian until mediaeval times, of a man and woman living together in a non-legalised relationship while observing vows of chastity.

Usage notes
The practice was often viewed with suspicion and disapproval. Females so "introduced" into a man's household were sometimes called virgines subintroductae — "virgins introduced secretly" — or simply ; other, less negatively loaded terms are and syneisaktoi.