double exposure

noun2

1. •
   A photograph produced by exposing film or some other photosensitive surface to focused light twice, usually by opening and closing a camera shutter two times, thereby generating a picture consisting of two superimposed images.

   • "The secret of all successful double-exposure photography may be expressed in one word—exactitude," said Georges Benoit, cameraman for Richard Walton Tully in The Masquerader. — 1922
2. •
   The process of producing such a photograph.

   • I've used double exposures to capture ghosts on film, to photograph two of me playing ping pong, and to capture a time-lapse shot of a birthday cake new and half-eaten in the same frame. — 2004