Definify.com
Webster 1913 Edition
Agonic
A-gon′ic
,Adj.
[Gr. [GREEK] without angles;
ἀ
priv. + [GREEK] an angle.] Not forming an angle.
Agonic line
(Physics)
, an imaginary line on the earth’s surface passing through those places where the magnetic needle points to the true north; the line of no magnetic variation. There is one such line in the Western hemisphere, and another in the Eastern hemisphere.