internal combustion engine
Definition from Wiktionary, the free dictionary
- A piston or a rotary heat engine directly powered by the products of intermittent combustion of a fuel.
- A heat engine in which intermittent or the continuous burning of a fuel takes place inside a combustion chamber; the resulting pressurized gas acts directly on the engine to do useful work, such as a piston engine, gas turbine, jet engine or rocket.
Related terms 
a piston or a rotary heat engine