The Collaborative International Dictionary of English v.0.48:

hologram \hol"o*gram\, n.
   A photographic image giving the observer a seemingly
   three-dimensional view of the represented object. The
   three-dimensional effect is produced by exposing a
   photographic recording medium to an interference pattern
   generated by a coherent beam of light (as from a laser)
   reflected from the subject, interacting with a beam directly
   from the source. The full three-dimensional effect requires
   illumination of the image with coherent light, but less
   perfect three-dimensional visual effects may also be observed
   when the hologram is illuminated with white light.
   [PJC]

WordNet (r) 3.0 (2006):

hologram
    n 1: the intermediate photograph (or photographic record) that
         contains information for reproducing a three-dimensional
         image by holography [syn: hologram, holograph]

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "hologram":
   Photostat, Xerox, Xerox copy, blowup, blueprint, contact printing,
   cyanotype, enlargement, glossy, lantern slide, matte, microcopy,
   microprint, photocopy, photogravure, photostatic copy, positive,
   print, projection printing, semi-matte, slide, transparency