Source : Webster's Revised Unabridged Dictionary (1913)

Azimuthal \Az"i*muth`al\, a.
   Of or pertaining to the azimuth; in a horizontal circle.

   {Azimuthal error} of a transit instrument, its deviation in
      azimuth from the plane of the meridian.

Source : WordNet®

azimuthal
     adj : of or relating to or in azimuth