any device that makes possible a finer setting of a tool or measuring instrument
adjective
of or fitted with a vernier
See vernier in American Heritage Dictionary 4
(vûrˈnē-ər)
noun
A small, movable auxiliary graduated scale attached parallel to a main graduated scale, calibrated to indicate fractional parts of the subdivisions of the larger scale, and used on certain precision instruments to increase accuracy in measurement. Also called vernier scale.
An auxiliary device designed to facilitate fine adjustments or measurements on precision instruments.