In reference to actors (William Shatner comes immediately to mind) chewing the scenery means overacting or over-emoting.
His expression of being shocked by the murder was so great he was chewing the scenery.
by Urban Nate December 03, 2009
1 more definition
To display excessive emotion or to act in an exaggerated manner while performing.
by 2tmfp9 July 10, 2011