Source : Webster's Revised Unabridged Dictionary (1913)

Aclinic \A*clin"ic\, a. [Gr. 'a priv. + ? to incline.]
   (Physics.)
   Without inclination or dipping; -- said the magnetic needle
   balances itself horizontally, having no dip. The aclinic line
   is also termed the magnetic equator. --Prof. August.