background color

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