heuristic

That employs a practical method not guaranteed to be optimal or perfect; either not following or derived from any theory, or based on an advisedly oversimplified one.

That provides a useful, but not optimal, solution to a problem. Such algorithms are typically employed either because the only known algorithms that provide optimal solutions use too much time or resources, or else because there is no known algorithm that provides an optimal solution.

That reasons from the value of a method or principle that has been shown by experimental investigation to be a useful aid in learning, discovery and problem-solving.