Wiktionary
rhumb lines
n. (rhumb line English)
Usage examples of "rhumb lines".
Scatflinger was lying on the gurney, quiescent, his head freshly shaved, blue lines drawn on his scalp like the rhumb lines of an ancient navigator.
In 1568 the Flemish geographer Gerhard Kremer (better known by the Latinized version of his last name, Mercator) put out a map of the world plotted in such a way that the rhumb lines were straight.
Maps for navigation based on Mercator's scheme could be easily marked with rhumb lines, and many of them were therefore put in, crossing and crisscrossing.
Hornblower's mind, if it was thinking about anything at all at that moment, was thinking about rhumb lines.