Rhumb \Rhumb\, n. [F. rumb, Sp. rumbo, or Pg. rumbo, rumo, probably fr. Gr. ??? 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.

To sail on a rhumb, to sail continuously on one course, following a rhumb line.

Source: Webster's Revised Unabridged Dictionary (1913)