aclinic line

[ey-klin-ik] /eɪˈklɪn ɪk/
noun
1.
an imaginary line on the surface of the earth, close and approximately parallel to the equator, connecting all those points over which a magnetic needle shows no inclination from the horizontal.
Also called magnetic equator.
Origin
1840-50; < Greek aklin(ḗs) not bending (a- a-6 + klin-, variant stem of klī́nein to bend) + -ic
British Dictionary definitions for aclinic line

aclinic line

/əˈklɪnɪk/
noun
1.
another name for magnetic equator
Word Origin
C19: aclinic, from Greek aklinēs not bending, from a-1 + klinein to bend, lean