Definify.com
Webster 1913 Edition
Instep
In′step
,Noun.
[Formerly also
instop
, instup
.] 1.
The arched middle portion of the human foot next in front of the ankle joint.
3.
That part of the hind leg of the horse and allied animals, between the hock, or ham, and the pastern joint.
Webster 1828 Edition
Instep
IN'STEP
,Noun.
1.
The instep of a horse, is that part of the hind leg, which reaches form the ham to the paster-joint.