The Collaborative International Dictionary of English v.0.48:

Aclinic \A*clin"ic\ ([.a]*kl[i^]n"[i^]k), a. [Gr. '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.
   [1913 Webster]