rhumb

n. [ F. rumb, Sp. rumbo, or Pg. rumbo, rumo, probably fr. Gr. &unr_;&unr_;&unr_; a magic wheel, a whirling motion, hence applied to a point of the compass. See Rhomb. ] (Navigation) A line which crosses successive meridians at a constant angle; -- called also rhumb line, and loxodromic curve. See Loxodromic. [ 1913 Webster ]

To sail on a rhumb, to sail continuously on one course, following a rhumb line. [ 1913 Webster ]