What is "water rocket"

Water rocket \Wa"ter rock"et\

1. (Bot.) A cruciferous plant ( Nasturtium sylvestre) with small yellow flowers.

2. A kind of firework to be discharged in the water.

n. A rocket that uses water as a propellant, which is forced out of the rocket by compressed gas (typically compressed air)

A water rocket is a type of model rocket using water as its reaction mass. Such a rocket is typically made from a used plastic soft drink bottle. The water is forced out by a pressurized gas, typically compressed air. Like all rocket engines, it operates on the principle of Newton's third law of motion.