S.S.O.

"Surrogate significant other" (male or female). Refers to a person in a relationship that is essentially identical to a boyfriend/girlfriend relationship, but with no sexual contact and no expectation of such. S.S.O.'s typically spend a very large amount of time together, have little inside secrets and jokes between them, and would seem to any outside observer to be "together".

One may have an S.S.O. to fulfill their some of their non-sexual emotional needs, while leaving them free to have sex with whomever else and however many others they want.

It is not unusual for one of the persons to be married or in a relationship. It is best for an S.S.O. to be attractive, because they are seen together all the time, but they shouldn't be sexually attracted to each other (at least not that much).