background color

Most terminals allow you to set an explicit background color for the plot. The special linetype bgnd will draw in this color, and bgnd is also recognized as a color. Examples:

     # This will erase a section of the canvas by writing over it in the
     # background color
     set term wxt background rgb "gray75"
     set object 1 rectangle from x0,y0 to x1,y1 fillstyle solid fillcolor bgnd
     # Draw an "invisible" line at y=0, erasing whatever was underneath
     plot 0 lt bgnd