The act of three or more people jacking off or fingering themselves or others in the same room. This group maybe be of mixed genders or only one gender.
Jim: Dude, I was at Elliot's house the other day and he got some chicks to come over and jack us off.
John: Is there always group masturbation at Elliot's?
Jim: Yeah it's Elliot's house. Amazing things happen all the time.