GAUGE n.
gauge used only for testing other similar gauges, and preserved as a reference, to detect wear of the working gauges. (c) (Railroads) See Note under Gauge, n., 5. -- Star gauge (Ordnance), an instrument for measuring the diameter of the bore of a cannon at any point of its length. -- Steam gauge, an instrument for me…
GRIND v.
To wear down, polish, or sharpen, by friction; to make smooth, sharp, or pointed; to whet, as a knife or drill; to rub against one another, as teeth, etc.
GROOVE n.
furrow, channel, or long hollow, such as may be formed by cutting, molding, grinding, the wearing force of flowing water, or constant travel; a depressed way; a worn path; a rut.