n. [ L. injectio : cf. F. injection. ] 1. The act of injecting or throwing in; -- applied particularly to the forcible insertion of a liquid or gas, by means of a syringe, pump, etc. [ 1913 Webster ]

2. That which is injected; especially, a liquid inserted thrown into a cavity of the body by a syringe or pipe; a clyster; an enema. Mayne. [ 1913 Webster ]

3. (Anat.) (a) The act or process of filling vessels, cavities, or tissues with a fluid or other substance. (b) A specimen prepared by injection. [ 1913 Webster ]

4. (Steam Eng.) (a) The act of throwing cold water into a condenser to produce a vacuum. (b) The cold water thrown into a condenser. [ 1913 Webster ]

Injection cock, or
Injection valve (Steam Eng.), the cock or valve through which cold water is admitted into a condenser. --
Injection condenser. See under Condenser. --
Injection pipe, the pipe through which cold water is through into the condenser of a steam engine. --
fuel injection, a method of inserting fuel into internal-combustion engines by directly forcing the liquid fuel into the combustion chamber at an appropriate point in the piston cycle; in contrast to carburetion, in which an air-fuel mixture is drawn in by the downward stroke of the piston. [ 1913 Webster +PJC ]