Definition of grand tours:
(n) :
(cycling) One of the three most prominent cycling races: either the Tour de France, Giro d'Italia and Vuelta a España.
(n) :
(historical, 17th-19th centuries) A traditional trip around Europe undertaken by mainly upper-class European young men.
(n) :
Alternative letter-case form of Grand Tour. [(cycling) One of the three most prominent cycling races: either the Tour de France, Giro d'Italia and Vuelta a España.]