What is "alydar"

Alydar (March 23, 1975 – November 15, 1990) was a chestnut colt and an American Thoroughbred race horse who was most famous for finishing a close second to Affirmed in all three races of the Triple Crown. With each successive race, Alydar narrowed Affirmed's margin of victory; Affirmed won by 1.5 lengths in the Kentucky Derby, by a neck in the Preakness and by a head in the Belmont Stakes. Alydar has been described as the best horse in the history of Thoroughbred racing never to have won a championship. Alydar's fame continued when he got older when he died under suspicious circumstances.