1. the act of concealing the existence of something by obstructing the view of it

e.g. the cover concealed their guns from enemy aircraft

Synonym: covercoveringscreening

2. scenery used to block the audience's view of parts of the stage that should not be seen

Synonym: masking piece

3. the blocking of one sensation resulting from the presence of another sensation

e.g. he studied auditory masking by pure tones