Source : Webster's Revised Unabridged Dictionary (1913)

Helispheric \Hel`i*spher"ic\, Helispherical \Hel`i*spher"ic*al\,
   a. [Helix + spheric, spherical.]
   Spiral.

   {Helispherical line} (Math.). the rhomb line in navigation.
      [R.]