Source : Free On-Line Dictionary of Computing

tail recursion
     
         When the last thing a function (or procedure)
        does is to call itself.  Such a function is called tail
        recursive.  A function may make several recursive calls but a
        call is only tail-recursive if the caller returns immediately
        after it.  E.g.
     
        	f n = if n < 2 then 1 else f (f (n-2) + 1)
     
        Here the both calls to fib are {recursive} but only the outer
        one is tail recursive.
     
        See {tail recursion optimisation}, and, if you aren't sick of
        them already, {recursion}, {tail recursion}.
     
        [{Jargon File}]
     
        (1996-02-22)