Home › Words › I › isoporisoporisopor means A line on a map that joins places of equal annual change in a geomagnetic property; an isoporic line.EtymologyFrom iso- + Ancient Greek πόρος (póros, “journey”), on the basis that isopors are "lines of equal travel".nounA line on a map that joins places of equal annual change in a geomagnetic property; an isoporic line.e.g.“Mapping of the isopors, or lines of equal magnetic change, by the Department disclosed a large number of isoporic foci where the change in the magnetic elements is taking place most rapidly.” — 1938, Cooperation in Research: Carnegie institution of Washington Publication no. 501:Definitions & examples from Wiktionary (CC BY-SA 3.0).