Definition of isogonic:
(adj) :
(cartography, navigation) Describing imaginary lines connecting points on the Earth's surface of identical magnetic declination.
(n) :
(cartography, navigation) An isogonic line; a curve connecting points on the Earth's surface whose magnetic declination is identical.
(adj) :
(geometry) Having equal angles.
(adj) :
(zoology) Exhibiting, or relating to, isogonism.