The Collaborative International Dictionary of English v.0.48:

Scrim \Scrim\, n.
   1. A kind of light cotton or linen fabric, often woven in
      openwork patterns, -- used for curtains, etc,; -- called
      also India scrim.
      [1913 Webster]

   2. pl. Thin canvas glued on the inside of panels to prevent
      shrinking, checking, etc.
      [1913 Webster]

WordNet (r) 3.0 (2006):

scrim
    n 1: a firm open-weave fabric used for a curtain in the theater