internal combustion engine

Short definition from Wiktionary

Noun

1. 1
   A piston or a rotary heat engine directly powered by the products of intermittent combustion of a fuel.
2. 2
   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.
3. 3
   Alternative form of internal combustion engine.