A line on a graph which best illustrates the relationship between a set of points, especially one drawn so as to minimize the deviations from the line by individual points; frequently attributive.
Origin
Late 19th century.
Definition of best fit in US English:
best fit
noun
Mathematics
A line on a graph which best illustrates the relationship between a set of points, especially one drawn so as to minimize the deviations from the line by individual points; frequently attributive.