glideslope

Short definition from Wiktionary

Noun

1. 1
   The portion of an instrument landing system which provides vertical guidance to an aircraft during an approach to landing.
2. 2
   The portion of an instrument landing system which provides vertical guidance to an aircraft during an approach to landing: The vertical descent profile produced by the ILS glideslope transmitters.
3. 3
   The approach path of an aircraft as it comes in to land.