an arc of the horizon expressed as the clockwise angle measured between a fixed point, e.g. true north or true south, and the vertical circle passing through the centre of an object
horizontal direction
azimuthal /-ʹmoohthl/ adj
azimuthally /-ʹmoohthli/ adv
[Middle English, ultimately from Arabic as-sumūt the azimuth, pl of as-samt the way]