1. [n]  a soft thread for cleaning the spaces between the teeth
2. [n]  a soft loosely twisted thread used in embroidery
3. [v]  use dental floss to clean; of teeth

FLOSS is a 5 letter word that starts with F.

1. \Floss\ (?; 195), n. [It. floscio flabby, soft, fr. L.
   fluxus flowing, loose, slack. See {Flux}, n.]
   1. (Bot.) The slender styles of the pistillate flowers of
      maize; also called {silk}.
   
   2. Untwisted filaments of silk, used in embroidering.
   
   {Floss silk}, silk that has been twisted, and which retains
      its loose and downy character. It is much used in
      embroidery. Called also {floxed silk}.
   
   {Floss thread}, a kind of soft flaxen yarn or thread, used
      for embroidery; -- called also {linen floss}, and {floss
      yarn}. --McElrath.
   
   

2. \Floss\, n. [Cf. G. floss a float.]
   1. A small stream of water. [Eng.]
   
   2. Fluid glass floating on iron in the puddling furnace,
      produced by the vitrification of oxides and earths which
      are present.
   
   {Floss hole}.
      (a) A hole at the back of a puddling furnace, at which the
          slags pass out.
      (b) The tap hole of a melting furnace. --Knight.
   
   

3. \Floss\, n.
   A body feather of an ostrich. Flosses are soft, and gray from
   the female and black from the male.