isogonic in British English
(ˌaɪsəʊˈɡɒnɪk) or isogonal (aɪˈsɒɡənəl)
adjective1. mathematics having, making, or involving equal angles
noun2. Also called: isogonic line, isogonal line, isogone physics an imaginary line connecting points on the earth's surface having equal magnetic declination