A tardeth was a creature known to the Drayans. It was big, hairy, and fearsome.
Tuvok was questioned in 2372 by Corin, an elderly Drayan, if Vulcans ever got scared, even if they were being chased by a "big hairy tardeth". The Vulcan stated that those circumstances were irrelevant, and that a Vulcan approached every situation logically. (VOY: "Innocence")