Not too happy with you using autism to call someone dumb, but I'll leave this up assuming it was just a one-off.
Definition of sash for Students. 1  1 : a frame for a pane of glass in a door or window. 2  2 : the movable part of a window.
n. 1. A piece of fabric or other material that hangs in a window or open space as a decoration, shade, screen, or divider. 2. Something that functions as or resembles a screen, cover, divider, or barrier: the curtain of mist before the mountain; a heavy curtain of artillery fire.