There is also waterjet and jet stream. Not uncommon dictionary of jet is narrow,forceful stream of fluid or the nozzle producing it. Taking that into account di

There is also waterjet and jet stream. Not uncommon dictionary of jet is narrow,forceful stream of fluid or the nozzle producing it. Taking that into account difference between jet and propeller in tube is matter of speed and compression. It's just that fuel combustion is one the most practical energy sources including for producing jets of gas.