reciprocating engine - an internal-combustion engine in which the crankshaft is turned by pistons moving up and down in cylinderscrankshaft - a rotating shaft driven by (or driving) a crank cylinder block, engine block, block - a metal casting containing the cylinders and cooling ducts of an engine; "the engine had to be replaced because the block was cracked" internal-combustion engine, ICE - 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 piston, plunger - mechanical device that has a plunging or thrusting motion |