The Collaborative International Dictionary of English v.0.48:

Projector \Pro*ject"or\, n. [Cf. F. projeteur.]
   1. One who projects a scheme or design; hence, one who forms
      fanciful or chimerical schemes. --L'Estrange.
      [1913 Webster]

   2. an optical instrument which projects an image from a
      transparency or an opaque image onto a projection screen
      or other surface, using an intense light and one or more
      lenses to focus the image. The term projector by itself is
      usually used for projection of transparent images by
      passing the light beam through the image; a projector
      which projects an image of an opaque object is now
      ususally referred to as an overhead projector. In
      projection of 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 balopticon,
      radiopticon, radiopticon, mirrorscope, etc.
      [Webster 1913 Suppl. +PJC]

   Slide projector a projector for displaying images from
      individual transparencies (slides), each mounted in a
      separate frame suited to the mechanics of the projector.


   movie projector a projector which displays a series of
      images from a roll of transparent film in rapid sucession,
      thus giving the impression of showing a scene with motion
      as it originally was recorded.

   overhead projector see projector[2], above. -->
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Radiopticon \Ra`di*op"ti*con\ (r[=a]`d[i^]*[o^]p"t[i^]*k[o^]n),
   n. [Radio- + stereopticon.]
   See Projector, above.
   [Webster 1913 Suppl.]