Many swingers argue that non-swingers have conflated the terms because of lack of understanding and that there are distinct differences among the terms with specific meanings as to number, intent, sexual orientation, and familiarity of the persons involved.
When a person is entered or penetrated in the vagina and/or anus by two people at the same time.
Technically this is a form of exhibitionism rather than "group sex" per se.Variations on this system exist that use case to convey more information.Within the BDSM and D/s subcultures, upper and lower case letters can signify dominant (or top) and submissive (or bottom), respectively.For example, MMF would signify a ménage à trois of two men and one woman in which the center male has sexual contact with the other male and the female, and in which it is not specified whether there is contact between the female and the other male.
MFMF (situation pictured in photo to right), on the other hand, implies no same-sex contact.
These codes consist of arrangements of the letters M (for male) and F (for female).