The Collaborative International Dictionary of English v.0.48:
Azimuthal \Az"i*muth`al\, a. Of or pertaining to the azimuth; in a horizontal circle. [1913 Webster] Azimuthal error of a transit instrument, its deviation in azimuth from the plane of the meridian. [1913 Webster]WordNet (r) 3.0 (2006):
azimuthal adj 1: of or relating to or in azimuth