Tribiadism (also known as tribadism or scissoring) is a form of lesbianism. In tribiadism two or more females will rub their vulva's against each other while being entangled with/into each other. The rubbing may involve female to female genital contact, but may also be against other body parts. When the woman squirts, the liquid is usually used as lubricant. Also, women may engage in tribiadism while they menstruate, hence using the blood as lubricant.
The two girls engaged in tribiadism last night. They got entangled and rubbed their pussy's against each other until the struck first blood, and used it as lube.