Rocket engine nozzle
A rocket engine nozzle is a nozzle used in a rocket engine to make the burning propellants go out faster and over a bigger area.
Nozzle shape
The difference between the skinniest part of the nozzle to where the burning fuel comes out is what makes the rocket work so well. The shape of the nozzle is important too, with the best nozzle angle being about 15 degrees, and a smooth angle for the nozzle.