Source : Webster's Revised Unabridged Dictionary (1913)

Injection \In*jec"tion\, n. [L. injectio : cf.F. injection.]
   1. The act of injecting or throwing in; -- applied
      particularly to the forcible throwing in of a liquid, or
      a["e]riform body, by means of a syringe, pump, etc.

   2. That which is injected; especially, a liquid medicine
      thrown into a cavity of the body by a syringe or pipe; a
      clyster; an enema. --Mayne.

   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.

   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.

   {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.

Source : WordNet®

injection
     n 1: the forceful insertion of a substance under pressure
     2: any solution that is injected (as into the skin) [syn: {injectant}]
     3: the act of putting a liquid into the body by means of a
        syringe; "the nurse gave him a flu shot" [syn: {shot}]

Source : Free On-Line Dictionary of Computing

injection
     
        1.  A {function}, f : A -> B, is injective or
        one-one, or is an injection, if and only if
     
        	for all a,b in A, f(a) = f(b) => a = b.
     
        I.e. no two different inputs give the same output (contrast
        many-to-one).  This is sometimes called an embedding.  Only
        injective functions have left inverses f' where f'(f(x)) = x,
        since if f were not an injection, there would be elements of B
        for which the value of f' was not unique.  If an injective
        function is also a {surjection} then is it a {bijection}.
     
        2.  An injection function is one which takes
        objects of type T and returns objects of type C(T) where C is
        some {type constructor}.  An example is
     
        	f x = (x, 0).
     
        The opposite of an injection function is a {projection}
        function which extracts a component of a constructed object,
        e.g.
     
        	fst (x,y) = x.
     
        We say that f injects its argument into the data type and fst
        projects it out.
     
        (1995-03-14)