For a "friend with fringe benefits".
A close friend of either sex, who is very intimate, not in as commited a relationship as marriage but not excluding to have all the benefits of a marriage such as cohabiting, sharing confidences, etc.
Some explanation:
It started out between my friend and me, as not wanting to call our relationship just '
friendship'. Besides, we had our families,
work and other commitments of social construct independent from and of each other. And we were too 'old' or 'old-fashined' to use the term boy friend/girlfriend, but not old fashioned enough to be prudish about a sexual relationship that happens when you
meet someone '
special'. Hence we were 'friends' but having a variety of 'fringe benefits'!