Word Study
pelorus
CIDE DICTIONARY
pelorus, n. [After Pelorus, said to have been Hannibal's pilot when he left Italy.].
An instrument similar to a mariner's compass, but without magnetic needles, and having two sight vanes by which bearings are taken, esp. such as cannot be taken by the compass. [Webster 1913 Suppl.]
OXFORD DICTIONARY
pelorus, n. a sighting device like a ship's compass for taking bearings.
Etymology
perh. f. Pelorus, reputed name of Hannibal's pilot
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