least squares

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun plural A method of determining the curve that best describes the relationship between expected and observed sets of data by minimizing the sums of the squares of deviation between observed and expected values.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a method of fitting a curve to data points so as to minimize the sum of the squares of the distances of the points from the curve