Aclinic
Aclinic (ȧ*klin"ik) , adjective
[Greek 'a priv. + kli`nein to incline.]
(Physics) Without inclination or dipping; -- said of the imaginary line near the earth's equator on which the magnetic needle balances itself horizontally, having no dip. The aclinic line is also termed the magnetic equator. — Prof. August