Plain English Meaning
An invisible sloping radio beam aimed up from near the runway. The aircraft's instruments show the pilot whether they are flying along that slope, too high, or too low, so they can descend at the right angle to land.
Full Definition
The glideslope is the vertical guidance component of an Instrument Landing System (ILS). It transmits a narrow radio beam angled upward from the runway touchdown zone — typically at about 3 degrees — that the aircraft's instruments use to show whether it is on, above, or below the correct descent path to the runway.
Context Anchor
Seen on instrument approach charts and on instruments during an instrument landing system .