"Founded in Paris on 20 July 1924, the World Chess Federation (Federation Internationale des Echecs, known as FIDE from its French acronym) was recognized by the International Olympic Committee as an International Sports Federation in 1999."
The International Olympic Committee would be a reasonable arbiter for the definition of the term "sport" and its inclusion and recognition of chess as a sport.
Chess swimming can be a sport... Players will play on a floating chessboard in swimming pool. Result is determined by chess and first person to retire to poolside loses by forfeit.