in Anatomy, the hind part of the foot. See Anatomy, No. 66.

Heel of a Horse, the lower hinder-part of the foot comprehended between the quarters and opposite to the toe. The heel of a horse should be high and large, and one side of it should not rise higher than the other upon the pastern. To recover the heels of a horse that is hoof-bound, you should take out his sole and keep his heels very wide, by which they will be restored in a month.

Heel of a Horseman. This being the part that is armed with the spur, the word is used for the spur itself: "This horse understands the heel well." To ride a horse from one heel to another, is to make him go sideways, sometimes to one heel and sometimes to another.

in the sea-language. If a ship leans on one side, whether she be aground or afloat, then it is said the heels a-starboard, or a-port; or that the heels off-wards, or to the shore; that is, inclines more to one side than to another.