Bay \Bay\, a. [F. bai, fr. L. badius brown, chestnutcolored; -- used only of horses.] Reddish brown; of the color of a chestnut; -- applied to the color of horses. {Bay cat} (Zo["o]l.), a wild cat of Africa and the East Indies ({Felis aurata}). {Bay lynx} (Zo["o]l.), the common American lynx ({Felis, or Lynx, rufa}).