masking

masking (http://definr.com/masking)

     adj : hiding from view; "speeding down the other lane beyond the
           masking truck"- T.H.White"; "a masking piece is a flat
           or curtain that hides part of the stage from the
           audience"
     n 1: the act of concealing the existence of something by
          obstructing the view of it; "the cover concealed their
          guns from enemy aircraft" [syn: cover, covering, screening]
     2: the blocking of one sensation resulting from the presence of
        another sensation; "he studied auditory masking by pure
        tones"
     3: scenery used to block the audience's view of parts of the
        stage that should not be seen [syn: masking piece]