The Collaborative International Dictionary of English v.0.48:

Polissoir \Po`lis`soir"\, n. [F.]
   1. A polishing or grinding implement or instrument.
      [Webster 1913 Suppl.]

   2. (Glass Making) A tool consisting of a flat wooden block
      with a long iron handle, used for flattening out split
      cylinders of blown glass.
      [Webster 1913 Suppl.]