A biscornu is a small, 8-sided, stuffed ornamental pincushion, usually made out of Aida cloth or linen. Embroidery or cross-stitch is used to decorate the top and bottom of the cushion. A button is typically secured in the center of the cushion to give a small depression on the top. Beads, tassels and other objects can decorate the biscornu. They are typically able to fit in the palm of your hand. The name is derived from a French adjective, meaning skewed, quirky or irregular.
Nice and understandable biscornu basics are here: http://www.prettyimpressivestuff.com/biscornu.htm