Dictionary Def:

sport
[spawrt, spohrt]  
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.

sport
[spawrt, spohrt]   Example Sentences Origin
sport
   [spawrt, spohrt] Show IPA
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.
6.
an object of derision; laughingstock.
7.
something treated lightly or tossed about like a plaything.
8.
something or someone subject to the whims or vicissitudes of fate, circumstances, etc.
9.
a sportsman.
10.
Informal . a person who behaves in a sportsmanlike, fair, or admirable manner; an accommodating person: He was a sport and took his defeat well.
11.
Informal . a person who is interested in sports  as an occasion for gambling; gambler.
12.
Informal . a flashy person; one who wears showy clothes, affects smart manners, pursues pleasurable pastimes, or the like; a bon vivant.
13.
Biology . an organism or part that shows an unusual or singular deviation from the normal or parent type; mutation.
14.
Obsolete . amorous dalliance.

adjective
15.
of, pertaining to, or used in sports  or a particular sport.
16.
suitable for outdoor or informal wear: sport clothes.

verb (used without object)
17.
to amuse oneself with some pleasant pastime or recreation.
18.
to play, frolic, or gambol, as a child or an animal.
19.
to engage in some open-air or athletic pastime or sport.
20.
to trifle or treat lightly: to sport with another's emotions.
21.
to mock, scoff, or tease: to sport at suburban life.
22.
Botany . to mutate.

verb (used with object)
23.
to pass (time) in amusement or sport.
24.
to spend or squander lightly or recklessly (often followed by away ).
25.
Informal . to wear, display, carry, etc., especially with ostentation; show off: to sport a new mink coat.
26.
Archaic . to amuse (especially oneself).
Idiom
27.
sport one's oak. oak ( def. 5 ) .

3.
diversion; recreation; pleasant pastime.

so basically any game may be considered a sport not just your althletic games

& how much athletic ability is required for fishing? Hardly any from what I recall as well as Golf, hardly sporty/athletic under your definition

yay ! playing monopoly is a sport, or darts isnt everyone can make up their own mind

Golf is hardcore sport I wake up the next morning sore as... Cant recall darts ever doing that X(