Can you do it in street clothes? If you can wear the uniform out to dinner, forget it. Goodbye bowling, goodbye golf.
Are you constantly being encouraged to smoke and drink while playing? See previous.
Do you need special high-tech shoes? Sport. Special patent-leather shoes? Nope.
How bad are the participants' haircuts? Hair bad enough to put out an opponent's eye means gen-u-ine sport. (If the players wear protective headgear, try this: How bad are the fans' haircuts?)
Does it require players to utter the word "shuttlecock?" Nah.
Is there a cult to the unnecessarily expensive equipment? Skiing, fly-fishing and the America's Cup are about catalog shopping, not sport.
Is there a separate "celebrity tour"? Is Joe Pesci on it? This is the opposite of sport.
Can you be hurt? Sport. Can you be killed? Sport. Can you be left feeling better about yourself and the life choices you've made? Oprah.
Does it involve a Frisbee, a Hacky Sack or a gun? Be serious.
Finally, can you make millions of dollars when you turn pro? If yes, then it is no longer a sport, it is televised entertainment.