the GNU version of the Collaborative International Dictionary of English
n. A kind of silk thread less glossy than floss, and spun from coarser material. It is much used in embroidery instead of floss.
The Century Dictionary and Cyclopedia
n. Ferret or floss-silk; grogram yarn of thread.
Word Usage
"Floss silk is generally used for other stitches because it covers the thread of the canvas better than purse silk; it is, however, often replaced by filoselle, which is a much cheaper material."