....in the third leg of a twelve-hour marathon of the previous season's America's Next Top Model.... I tried my level best to get out of Support Group while sitting on the couch with my mom in the third leg of a twelve-hour marathon of the previous season's America's Next Top Model.... From the book, The Fault In Our Stars. What does "the third leg" mean here? Can you help me? It certainly does not refer to men's sexual organ.