It is also used to refer to an arrangement where three people share sexual relations, and this has become the predominant definition. Some also use it to describe any sex act involving three people, otherwise known as a threesome. Ménage à trois, two women with one man, has become more common, perhaps due to its presentation in porn films. There are ménage à trois arrangements involving two men and one woman, and these are also becoming more common.
Sometimes ménage à trois is called Hot Wives, referring to a married woman who has sex with men other than her spouse, with the husband's consent. In most cases the husbands take a vicarious pleasure in their wives' enjoyment, or enjoy watching, hearing, or knowing about their wives' adventures. Husbands may also take part by engaging in threesomes, or arranging dates for their wives.
Friend: "One of her girl friends?"
Boyfriend: "Nah man, one of her guy friends!"