1. an optical device for projecting a beam of light
2. an optical instrument that projects an enlarged image onto a screen
3. One who projects a scheme or design; hence, one who forms fanciful or chimerical schemes.
4. An optical instrument for projecting a picture upon a screen, as by a magic lantern or by an instrument for projecting (by reflection instead of transmission of light) a picture of an opaque object, as photographs, picture post-cards, insects, etc., in the colors of the object itself. In this latter form the projection is accomplished by means of a combination of lenses with a prism and a mirror or reflector. Specific instruments have been called by different names, such as radiopticon, mirrorscope, balopticon, etc.