From Voyeurweb's Wiki

[edit] DTS - Double Tit Sucking

This game is played by a single wife and two, generally men, partners. The guys are at the female's sides sucking on her boobs at the same time, frequently swapping position in order to have the opportunity to eat each boob. This is a variant of the MFM activity but is best played in MMFM combination with the third guy between the wife's legs, licking her clit or her pussy hole. Frequently, when wives play this game, none of their partners are the husbands; usually hubbys look at their wives being serviced by other guys and take pictures.