DuckCorp Dico

Found one definition

1.                 From WordNet (r) 3.0 (2006):
                   
   
   
                   
                     
   masking
       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, masking]
       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,
          masking]