Definitions for "Line of best fit"
A line drawn through the points in a scatter diagram. It yields the best prediction of one variable when given the value of the other variable.
A straight line used as a best approximation of a summary of all the points in a scatter-plot* (See definition below). The position and slope of the line are determined by the amount of correlation* (See definition above) between the two paired variables involved in generating the scatter-plot. This line can be used to make predictions about the value of one of the paired variables if only the other value in the pair is known.
a line plotted on a scatter plot of data (using a least-squares method) which is `closest to most points' of the plot.