I forget where I got this, but in my mind there are four criteria for being a sport:

1) It is a competitive, rules-based game.

2) It involves physical still (strength, dexterity, or endurance).

3) There are two or more competitors whose play directly influences the play of other(s).

4) The rules are enforced by a separate, impartial, objective arbiter.

This simple rubric makes it easy to classify any game as either Sport or Non-Sport, but tends to produce controversial results.. For example:

Sport: Auto Racing, most competitive "e-Sports", Boxing/MMA, Curling, Billiards/Snooker, Fencing

Non-Sports: Bowling, Golf, Pinball, Darts, Competitive Eating, Track & Field, most Olympic sports involving judges like Diving or Gymnastics

This is not to say that I think any less of what I'm calling "Non-Sports", or think they're any less entertaining, demanding, competitive, or worth doing.. Just wanted to share my criteria, and I'm happy to hear feedback/updates/suggestions to make it better.