Floss \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.