Source : Free On-Line Dictionary of Computing

call-by-name
     
        (CBN) (Normal order reduction, leftmost, outermost reduction).
        An argument passing convention (first provided by {ALGOL 60}?)
        where argument expressions are passed unevaluated.  This is
        usually implemented by passing a pointer to some code which
        will return the value of the argument and an environment
        giving the values of its {free variable}s.  This {evaluation
        strategy} is guaranteed to reach a {normal form} if one
        exists.
     
        When used to implement {functional programming} languages,
        call-by-name is usually combined with {graph reduction} to
        avoid repeated evaluation of the same expression.  This is
        then known as {call-by-need}.  The opposite of call-by-name is
        {call-by-value} where arguments are evaluated before they are
        passed to a function.  This is more efficient but is less
        likely to terminate in the presence of infinite data
        structures and {recursive} functions.  Arguments to {macro}s
        are usually passed using call-by-name.
     
        (1994-11-29)