calliper (caliper) (kal-i-per) n.
1. an instrument with two prongs or jaws, used for measuring diameters, particularly of the pelvis in obstetrics.

2. (calliper splint) a surgical appliance (see orthosis) that is used to correct or control deformity of a joint in the leg. It consists of a metal bar that is fixed to the shoe and held to the leg by means of straps.

calliper (usu. pl.) XVI. orig. calliper compasses compasses used for measuring the calibre of a bullet, etc.; presumably var. of CALIBRE.