Whilst in a car ride on the way back from a FIRST competition (AKA robotics competition), a friend of mine claimed robotics was a sport. To which, someone else pointed out that 'sport' is an impossible-to-define word, because no matter what definition you give it, somebody will provide an example of something that fits within your definition of the word, but contradicts the commonly accepted view of a 'sport'. So I challenge any willing soul to try to come up with an 'un-contradictable' definition for the term 'sport'.
Ex:
definition from Webster's dictionary: 'physical activity engaged in for pleasure'
My argument: Sex is also a physical activity engaged in for pleasure, and is not (yet) a sport.