SASH or WINDOW SASH

  1. A single light frame containing one or more lights of glass. The frame that holds the glass in a window, often the movable part of the window. 
  2. The operating or movable part of a window; the sash is made of window panes and their border

EXAMPLE:

Away to the window I flew like a flash, tore open the shutters and threw up the sash.” -The Night Before Christmas