Continuous sexual activity of any nature that is performed over the course of several hours. Even several days. To be a marathon, only short breaks in sex play activity like short sleep breaks, a power nap, a food break, bathroom break or fluid wipe ups are permitted. Sexual marathons often result in extremely sore genetalia.
Roger's wife had a hella sore snatch after an all night sex marathon.
by Harry Klam April 20, 2015