(亦作 rhumb line)an imaginary line on the earth's surface cutting all meridians at the same angle, used as the standard method of plotting a ship's course on a chart 恒向线
any of the 32 points of the compass 罗经方位
语源
late 16th cent.: from French rumb (earlier ryn (de vent) 'point of the compass'), probably from Dutch ruim 'space, room'. The spelling change was due to association with Latin rhombus (see rhombus)