Excuse me, for something as generic as "sport", a dictionary can not adequately define it. It's like a dictionary attempting to define "marriage" as union between a man and woman. That's a lot different than the definition of a word with a concrete meaning.
Besides, I agree with the dictionary definition in this case of "sport".
I know what you mean.. really. You're considering 'Athletic Competition' as sport. The problem is what constitutes an athlete. Almost like the tomato is fruit or vegetable argument. And, denizens of this forum like to poke and prod all the hot buttons.
There are the given 'sports' as defined as Athletic Competition.. football, baseball, gymnastics, hockey..etc. Racing, where as 'Joe Average' might just see a guy sitting down, doing a little steering and shifting every now and then, I would guess there is a bit of endurance being able to keep your wits about you long enough while pushing the lateral G tolerance for hours on end.. so, a certain amount of athleticism is probably necessary to be a GOOD driver. And this would apply to motorcycles, as well.
And for those who don't believe 'Competitive Cheerleading' is done by athletes, I demand that you observe, for 2 weeks, the level of training/practice that any of the top 'level 5' clubs conduct before you pass judgement. This level is where they're doing stunting and serious tumbling ( double fulls, whips, aerials, .. etc ).
Personally, I wouldn't belittle the effort necessary to be proficient at any 'sport' until I've mastered it myself. Walk a mile in their shoes, so to speak.