Real Dictionary

internal combustion engine
an engine, as in an airplane, automobile, etc., that obtains its power from heat and pressure produced by the combustion of a fuel-and-air mixture inside a closed chamber or cylinder
countable noun: An internal combustion engine is an engine that creates its energy by burning fuel inside itself. Most cars have internal combustion engines.
noun: a heat engine in which heat is supplied by burning the fuel in the working fluid (usually air)
noun: an engine of one or more working cylinders in which the process of combustion takes place within the cylinders

internal combustion engine in Automotive Engineering
noun: An internal combustion engine is an engine that creates its energy by burning fuel inside itself. Most cars have internal combustion engines.