touchdown

touchdown

1. the moment at which a landing aircraft or spacecraft comes into contact with the landing surface

2. Rugby the act of placing or touching the ball on the ground behind the goal line, as in scoring a try

3. American football a scoring play worth six points, achieved by being in possession of the ball in the opposing team's end zone

Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

touchdown

i. The point where the nominal glide path intercepts the runway (ICAO). In this case, this point is only a datum and is not necessarily the actual point at which the aircraft will touch the runway.
ii. In a precision radar approach, the point on the landing surface toward which the controller issues guidance instructions.
iii. The contact, or moment of contact, an aircraft makes with the landing surface—land or water—and ceases to be airborne.

An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved