friendcestuous
Like incestuous, but with your friends. A group of friends that's oddly, freakishly close with each other. Hold hands, occasionally kiss, share toothbrushes. Sometimes significant others of the friends get jealous of how touchy feely they are.
Those girls over there are so friendcestuous. It's kinda hot, actually. They keep cuddling and licking each other.
Friendcestuous
A word to describe a person or people who sleeps with and/or dates several different friends within the same social circle.
She is so friendcestuous, she has slept with every single one of her single guy friends, and they are all friends with each other.