The Collaborative International Dictionary of English v.0.48:

Internal-combustion engine \Internal-combustion engine\) in
   which the heat or pressure energy necessary to produce motion
   is developed in the engine cylinder, as by the explosion of a
   gas, and not in a separate chamber, as in a steam-engine
   boiler. The gas used may be a fixed gas, or one derived from
   alcohol, ether, gasoline (petrol), naphtha, oil (petroleum),
   etc. There are three main classes: (1) gas engines proper,
   using fixed gases, as coal, blast-furnace, or producer gas;
   (2) engines using the vapor of a volatile fluid, as the
   typical gasoline (petrol) engine; (3) oil engines, using
   either an atomized spray or the vapor (produced by heat) of a
   comparatively heavy oil, as petroleum or kerosene. In all of
   these the gas is mixed with a definite amount of air, the
   charge is composed in the cylinder and is then exploded
   either by a flame of gas (flame ignition -- now little used),
   by a hot tube (tube ignition) or the like, by an electric
   spark (electric ignition, the usual method is gasoline
   engines, or by the heat of compression, as in the Diesel
   engine. Gas and oil engines are chiefly of the stationary
   type. Gasoline engines are largely used for automobile
   vehicles, boats, etc. Most internal-combustion engines use
   the Otto (four-stroke) cycle, though many use the two-stroke
   cycle. They are almost universally trunk engines and
   single-acting. Because of the intense heat produced by the
   frequent explosions, the cylinders must be cooled by a water
   jacket (water-cooled) or by air currents (air cooled) to give
   the maximum thermodynamic efficiency and to avoid excessive
   friction or seizing.
   [Webster 1913 Suppl.] internalise \internalise\ v.
   (Psychology)
   Same as internalize. MKChiefly Brit.

   Syn: internalize, interiorize, interiorise.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

internal-combustion engine
    n 1: a heat engine in which combustion occurs inside the engine
         rather than in a separate furnace; heat expands a gas that
         either moves a piston or turns a gas turbine [syn:
         internal-combustion engine, ICE]