x-ray

n. & v. (also x-ray)
—n.
1 (in pl.) electromagnetic radiation of short wavelength, able to pass through opaque bodies.
2 an image made by the effect of X-rays on a photographic plate, esp. showing the position of bones etc. by their greater absorption of the rays.
—v.tr. photograph, examine, or treat with X-rays.
Phrases and idioms:
X-ray astronomy the branch of astronomy concerned with the X-ray emissions of celestial bodies. X-ray crystallography the study of crystals and their structure by means of the diffraction of X-rays by the regularly spaced atoms of a crystalline material. X-ray tube a device for generating X-rays by accelerating electrons to high energies and causing them to strike a metal target from which the X-rays are emitted.
Etymology: transl. of G x-Strahlen (pl.) f. Strahl ray, so called because when discovered in 1895 the nature of the rays was unknown