the ankle bone, or hock bone; the bone of the tarsus which articulates with the tibia at the ankle.-a genus of papilionaceous plants, of the tribe galegeae, containing numerous species, two of which are called, in english, milk vetch and licorice vetch. gum tragacanth is obtained from different oriental species, particularly the a. gummifer and a. verus.-see astragal, 1.