A blind contour drawing is one in which you don't look at the drawing surface and never stop the movement of your pen.

After a few blind contour sketches of my partner (shown below) I chose the third drawing because I immediately saw the emotion contained within the face.

Part of the project was to have at least part of the design resemble the person sketched, so I put the woman's hair in a bun, and clothed her in a turtleneck sweater similar to the one my partner was wearing that day.  The rest of the lines, as you can see from my sketch below, came directly from the blind contour  sketch.