Definition
The shaped opening at the rear of a turbojet or turbofan engine through which exhaust gases are discharged at high velocity to produce thrust. The nozzle's converging shape accelerates the exhaust flow, converting pressure and heat energy into kinetic energy.
Plain English
The narrowed opening at the back of a jet engine where the hot exhaust shoots out. Squeezing the flow through this opening speeds it up, and that fast-moving gas is what pushes the aircraft forward.
Context Anchor
Seen in turbine engine descriptions, exhaust system inspections, and discussions of how jet engines produce thrust.
Derivation
From the French 'jet' (a stream or spurt) and 'nozzle' (a small spout, from Old English 'nosu' meaning nose). Together it describes the 'nose' of the engine from which the stream of exhaust gas spurts.
Why Pilots Care
Controls how efficiently exhaust gases produce thrust; damage or improper operation reduces engine power and increases fuel burn.
Analogy
Like putting your thumb partly over the end of a garden hose. The same amount of water is flowing, but squeezing the opening makes it shoot out faster and harder.
Intuition Check
Do not think of a jet nozzle as just an open pipe. It is a shaped outlet designed to control direction and speed of the exhaust flow.
Example Sentence 1
During the walk-around, the pilot inspected the jet nozzle for any signs of cracking or hot-spot damage.
Example Sentence 2
Variable jet nozzles open wider at high speed to maintain efficient exhaust flow.