Nuclear rocket and Rocket engine

Nuclear rocket noun - A rocket engine in which a nuclear reactor is used to heat a propellant.

Rocket engine and nuclear rocket are semantically related. In some cases you can use "Rocket engine" instead a noun phrase "Nuclear rocket".

Rocket engine noun - A jet engine containing its own propellant and driven by reaction propulsion.

Nuclear rocket and rocket engine are semantically related. Sometimes you can replace phrase "Nuclear rocket" with "Rocket engine", this phrases are similar.