a gauge that measures small distances or thicknesses between its two faces, one of which can be moved away from or towards the other by turning a screw with a fine thread.
A lineal measure in the metric system, containing the thousandth part of a meter; equal to .03937 of an inch. See 3d Meter.
An instrument, used with a telescope or microscope, for measuring minute distances, or the apparent diameters of objects which subtend minute angles. The measurement given directly is that of the image of the object formed at the focus of the object glass.