shadowgraph

noun
  1. 1

    A shadow-picture; a radiograph or X-ray photograph; a sciagram.

  2. 2

    An optical technique of visualizing patterns of fluid flow by using differences in refractive index

verb
  1. 1

    To outline in a shadow-picture on a screen.

  2. 2

    To take a picture by means of X-ray, radium, or similar source of actinic radiation.

Source: https://en.wiktionary.org/wiki/shadowgraph