Rocket. The word refers to that tall, slim vehicle on a launchpad ready to fly into space.
It also refers to the engine that takes the vehicle there. Rocket engines can be large, like the one in a spacecraft, or small. They may have great power or limited power. They may send an object great distances or not. Rocket engines have all these differences, but they all have this in common: They work by burning fuel, turning it into hot gas, and pushing it out the back to produce thrust, the force that moves the object.