a sighting device used in conjunction with a magnetic compass or a gyrocompass for measuring the relative bearings of observed points
Word origin
of uncertain origin, perhaps from Latin Pelōrus a dangerous Sicilian promontory
pelorus in American English
(pəˈloʊrəs; pəˈlɔrəs)
noun
Nautical
a device for taking bearings, consisting of a flat metal ring, equipped with sighting vanes or a small telescope, that fits over a compass card or gyrocompass