What is "profilometer"

n. A device designed to measure the profile, and hence the roughness, of a surface

Profilometer is a measuring instrument used to measure a surface's profile, in order to quantify its roughness.

While the historical notion of a profilometer was a device similar to a phonograph that measures a surface as the surface is moved relative to the contact profilometer's stylus, this notion is changing with the emergence of numerous non-contact profilometery techniques.