X-ray

• POS: Noun, Verb (transitive)

CIDE DICTIONARY

X-ray, n. [so called by its discoverer because of its enigmatical character, x being an algebraic symbol for an unknown quantity.].

 originally, any of the rays produced when cathode rays strike upon surface of a solid (as a copper target or the wall of the vacuum tube); now defined as electromagnetic radiation with a wavelength of 0.1 to 10 nanometers. X-rays are noted for their penetration of many opaque substances, as wood and flesh, their action on photographic plates, and their fluorescent effects. They were called X rays by their discoverer, W. K. Röntgen, but were also referred to for some time as Roentgen rays. The term X-ray has become the most common designation. They also ionize gases, but cannot be reflected, or polarized, or deflected by a magnetic field. They are used in examining objects opaque to visible light, as for imaging bones or other structures inside the human body, and for detecting flaws in metal objects, such as in welds.  [Webster 1913 Suppl.]

X-ray, v. t. 

 to examine by means of X-rays; to irradiate with X-rays.  [PJC]

OXFORD DICTIONARY

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.

Idiom

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