Dictionary.com definition
-a. Physical activity that is governed by a set of rules or customs and often engaged in competitively.
-b. A particular form of this activity.
-c. An activity involving physical exertion and skill that is governed by a set of rules or customs and often undertaken competitively.
-d. An active pastime; recreation.
RC- physical activity unless you have figured out how to control your car with your mind.
RC-Rulesand customs
RC-Competetitive
Physical exertion is questionable unless youve gone to any big races and spent 3 to 5 days racing on 3 hrs sleep a day.
My opinion is that some do it as a sport and some do it as a hobby it depends on your level of involvement. Any sport can be somebody elses hobby.