Source : Free On-Line Dictionary of Computing

A* search
     
         A {graph} search {algorithm}.  A* is guaranteed to
        find a minimal solution path before any other solution paths,
        if a solution exists, in other words, it is an "{admissible}"
        search algorithm.  Each path is assigned a value based on the
        cost of the path (e.g. its length) and an (under)estimate of
        the cost of completing the path, i.e. the cost of a path from
        the end of the current path to a solution.
     
        (1995-03-31)