Source : Webster's Revised Unabridged Dictionary (1913)

Isoclinal \I`so*cli"nal\, Isoclinic \I`so*clin"ic\, a. [Iso- +
   Gr. ? to incline.]
   Of or pertaining to, or indicating, equality of inclination
   or dip; having equal inclination or dip.

   {Isoclinal lines} (Magnetism), lines on the earth's surface
      connecting places at which a dipping needle indicates the
      same inclination or dip.