Source : Webster's Revised Unabridged Dictionary (1913)

Heuristic \Heu*ris"tic\, a. [Gr. ? to discover.]
   Serving to discover or find out.

Source : WordNet®

heuristic
     adj : of or relating to or using a general formulation that serves
           to guide investigation [ant: {algorithmic}]
     n : a commonsense rule (or set of rules) intended to increase
         the probability of solving some problem [syn: {heuristic
         rule}, {heuristic program}]

Source : Free On-Line Dictionary of Computing

heuristic
     
        1.  A rule of thumb, simplification, or educated
        guess that reduces or limits the search for solutions in
        domains that are difficult and poorly understood.  Unlike
        {algorithms}, heuristics do not guarantee optimal, or even
        {feasible}, solutions and are often used with no theoretical
        guarantee.
     
        2.  {approximation algorithm}.
     
        (2001-04-12)