PILOT'S ABBR. is an acronym for three navigational directions used by pilots: ALT (3 letters) stands for Altitude, NNE (3 letters) stands for North-Northeast, and SSE (3 letters) stands for South-Southeast. Altitude is the vertical distance of a location above sea level, while North-Northeast and South-Southeast are two of the four cardinal directions used to describe a location's relative position on a map.