Dictionary.com Shadow 1. An area that is not or is only partially irradiated or illuminated because of the interception of radiation by an opaque object between the area and the source of radiation. 2. The rough image cast by an object blocking rays of illumination. See Synonyms at shade. 1. Unlit room, the light source is outside the room and the walls are casting shadows in the room (technically speaking :)....just playing devil's advocate) 2. the common idea of a shadow.