A scatter-plot or residual plot shows homoscedasticity if the scatter in vertical slices through the plot does not depend much on where you take the slice
                                                            
                                                     
                        
                                                
                        
                        
                            Time-independent variance. The GARCH Toolbox also refers to homoscedasticity as constant conditional variance.
                                                            
                                                     
                        
                                                
                        
                        
                            The variance of the Y scores in a correlation are uniform for the values of the X scores. In other words, the Y scores are equally spread above and below the regression line.