If both a husband and wife are mutually consenting to bringing in a 3rd or 4th or 5th person into their bedroom (metaphorically speaking) for the purpose of adding another level of excitement and stimulation into their maritial sexlife, then then that is swinging.
Whether the two couples "cross-pollinate" and have intercourse with the other couple's spouse is just a matter of degree of swinging but two women having sexual contact while the husbands consent and watch and then enjoy the extra sexual excitement would fall within the realm of swinging.Just for future reference, that is often called "soft swing" or simply "F/F-only" in the swinging world. Intercourse between male and female of different couples is "full swap" and male/female contact without intercourse is called "soft swap"
