| an imaginary line on the surface of the earth connecting all points at which the declination of the magnetic field of the earth is zero. |
| agonic line n. An imaginary line on the earth's surface connecting points where the magnetic declination is zero. |
agonic line  (ā-gŏn'ĭk) Pronunciation Key
An imaginary line on the Earth's surface connecting points where the magnetic declination is zero. The agonic line is a line of longitude on which a compass will show true north, since where magnetic declination is zero, magnetic north coincides with geographic north. |