Water rocket : A cruciferous plant (Nasturtium sylvestre) with small yellow flowers.

Water rocket : A kind of firework to be discharged in the water.

Example:


Taxonomy
rocket, water rocket, nozzle, bottle, rocket nozzle, pressure, gas, bottle rockets, thrust, competition, launch tube, flights, rocket competition, rocket engines, pressurized, compressed air, tubes, psi.

Defination from the web:
rocket—is usually a used plastic soft drink bottle. The water is forced out by a pressurized gas, ... The seal on the nozzle of the rocket is then released and rapid expulsion of water occurs at high speeds until the propellant has been used up ...