As defined by the Merriam-Webster dictionary sport is a physical activity engaged in for pleasure, or a particular activity such as an athletic game.
However I must say this question of "exactly what is a sport" has come up more than once in my home and the best definition I’ve found was that of my older brothers:
A sport is something that cannot be beat whereas a game can.
What this means is that the major professional sports (football, baseball, basketball, and I guess I’ll even throw in soccer) fall under this preferred definition as a sport.
In these sports the object is not to beat the game but to beat the opponent. However a game like golf or bowling is just that, a game. In these games the object is not to beat the opponent it’s to beat the game.
In golf there’s par: you get under par, you’ve beat the hole; stay under par the whole course, you’ve beat the course.
In the case of the video game, even when played with an opponent, because you’re still playing the game itself it’s not a sport.
Most games are made with the intent of the human playing the computer, this is the case in most war games or role playing games where the goal is to beat the game.
You can point out that in most fighting games and sport games you can play an opponent but even in those a bulk of the game is intended for the human to play the computer.
That’s why arcade mode comes before versus and dynasty modes are made so elaborate because those are the intended paths of play.
Where this definition becomes tricky is in the case of something like poker, it’s easy to make the argument that the object of the game is to beat the opponent, making it a sport under this definition.
However I can’t bring myself to allow this particular game to be called a sport. So I’ll adapt my definition, if only to keep poker out of the sport category, and change it to…
A sport is a physical activity or game that cannot be beat.
This eliminates poker, and pretty much any other game you can play by yourself. So there you have it the official Ken Sheehan definition that makes things like football, soccer, and badminton sports and defines games such as poker solitaire and golf as just that.