Definitions from Dictionary.com:
Sport (noun)
1. an athletic activity requiring skill or physical prowess and often of a competitive nature, as racing, baseball, tennis, golf, bowling, wrestling, boxing, hunting, fishing, etc.
2. a particular form of this, especially in the out of doors.
3. diversion; recreation; pleasant pastime.
4. jest; fun; mirth; pleasantry: What he said in sport was taken seriously.
5. mockery; ridicule; derision: They made sport of him.
Hobby (noun)
1. an activity or interest pursued for pleasure or relaxation and not as a main occupation: Her hobbies include stamp-collecting and woodcarving.
2. a child's hobbyhorse.
3. Archaic. a small horse.