A line on the earth's surface crossing all meridians at the same angle, synonymous with a rhumb line course.
In practice
In practical navigation, the loxodrome is the default route for coastal and short-range ocean passages because a constant compass course steered with reference to the gyrocompass accurately traces a rhumb line across the chart. The distinction between loxodrome and great circle becomes significant only at higher latitudes and over long distances; on passages across the North Atlantic or North Pacific, for example, the great-circle savings can amount to hundreds of miles. The OOW preparing a passage plan compares loxodromic and great-circle distances, using ECDIS tools or printed tables, and chooses the route that best balances economy with weather and navigational safety.
Regulatory detail & full definition
A loxodrome is the technical term for a curve on the earth's surface that cuts every meridian at the same angle, synonymous with a rhumb line. The name derives from Greek (loxos, oblique; dromos, course). On a Mercator chart, a loxodrome appears as a straight line, which makes it operationally convenient for chart work and constant-course steering. Bowditch (American Practical Navigator) discusses the loxodrome in the context of Mercator sailing, where the difference in meridional parts between two latitudes allows precise calculation of course and distance along the loxodrome.
In practical navigation, the loxodrome is the default route for coastal and short-range ocean passages because a constant compass course steered with reference to the gyrocompass accurately traces a rhumb line across the chart. The distinction between loxodrome and great circle becomes significant only at higher latitudes and over long distances; on passages across the North Atlantic or North Pacific, for example, the great-circle savings can amount to hundreds of miles. The OOW preparing a passage plan compares loxodromic and great-circle distances, using ECDIS tools or printed tables, and chooses the route that best balances economy with weather and navigational safety.