Yearling n. : An animal one year old, or in the second year of its age; -- applied chiefly to cattle, sheep, and horses.

Yearling a. : Being a year old.

Example:
How to get a Yearling to in a circle on a lead line?

Taxonomy
yearlings, horse, free encyclopedia, colt, Weanling, race horses, saddle, Ensminger, Tack, Volume Reference, Boston, Houghton Mifflin Co, male horse, filly, female horse, Types of horses, search, one and two.

Defination from the web:
yearling will have already been trained as a suckling or weanling foal to lead, to have its hooves handled, to be ... If these tasks have not been accomplished, the yearling year is a time they are often done, in part to get the horse used to human handling ...