RhymeZone: isocline definitions

Definitions of isocline:

noun: (geology) A tightly folded syncline or anticline in which the two sides are almost parallel.
noun: (geography, mathematics) A line, curve or function on a graph or map linking points with the same slope or gradient.
noun: (geography) A line on a map linking places with the same magnetic dip; an isoclinic line.

(Definitions from Wiktionary)