a running race that is half the distance of a marathon, i.e. 13.1 miles
person 1 "Hey I saw you running yesterday! Are you on cross country or something?"
person 2 "Yeah, but we don't race more than a few miles at cross country, I'm training for a half marathon"
person 1 "Wow, that's a lot of running!"
A sexual position where a female clings upside down to a male's front and sucks his genitalia (or a blowjob ) whilst he runs on the spot. If said female chokes or is sick, this is known as a Paula Radcliffe.
Cat: want to try some sick new sex moves tonight?
Matt: sure, like what?
Cat: the half marathon?
Matt: sounds like fun!