rare, historical Relating to or designating a navigational course in which a ship follows a rhumb line, i.e., a course which cuts meridians at a constant angle (other than a right angle). Chiefly in "paradoxal compass" noun a projection on which such a course could be plotted, and on which it would appear as part of a spiral curve.
2 rare Generally. Paradoxical.
Mid 16th century; earliest use found in John Dee (1527–1609), mathematician, astrologer, and antiquary. From paradox or its etymon classical Latin paradoxum + -al.