marathon sex means: If the sex lasts more than an hour with continuing intent, it is considered to be sex. Partners may not have any distractions during sex if they are only for an hour and half. Small breaks may be taken during’marathon sex’, as opposed to marathons. However, this is still exercise for both the partners in all cases. (in Community Dictionary, added by Lindsay Marshall)

What else does marathon sex mean?

  • Not having sex with more than three people in a single night. Every session lasting longer than one hour. (in Community Dictionary, added by Susana Díaz)
  • The sessions last for several hours, with intermissions in which the participants sweatily try to return the blood oxygen-carbon dioxide mixture. It’s a session that can burn as much as a marathon. (in Community Dictionary, added by Asher Rasmussen)