What is "durometer"

Durometer \Du*rom"e*ter\, n. [L. durus hard + -meter.] An instrument for measuring the degree of hardness; especially, an instrument for testing the relative hardness of steel rails and the like.

n. An instrument used to measure the hardness or stiffness of a material, especially of an elastomer, such as rubber. A simple durometer consists of a movable tip on a spring with a dial gauge.