The Collaborative International Dictionary of English v.0.48:

Sash \Sash\, n. [F. ch[^a]ssis a frame, sash, fr. ch[^a]sse a
   shrine, reliquary, frame, L. capsa. See Case a box.]
   1. The framing in which the panes of glass are set in a
      glazed window or door, including the narrow bars between
      the panes.
      [1913 Webster]

   2. In a sawmill, the rectangular frame in which the saw is
      strained and by which it is carried up and down with a
      reciprocating motion; -- also called gate.
      [1913 Webster]

   French sash, a casement swinging on hinges; -- in
      distinction from a vertical sash sliding up and down.
      [1913 Webster]