Between one's Weenis and another's Wagina. Not at all stimulating. Rubbing one's Weenis with said person's Wagina is "Elbow Masturbation"
Hey did you hear who had Elbow sex yesterday?
when two or more people rub their elbows together on pupose.
Bill and I were walking in the mall when our elboys rubbed together, so we stopped and rubbed them together faster yelling 'elbow sex'.