electromagnetic radiation emitted when matter is bombarded with fast electrons. X-rays have wavelengths shorter than that of ultraviolet radiation, that is less than about 1 × 10–8 metres. They extend to indefinitely short wavelengths, but below about 1 × 10–11 metres they are often called gamma radiation
a picture produced by exposing photographic film to X-rays: used in medicine as a diagnostic aid as parts of the body, such as bones, absorb X-rays and so appear as opaque areas on the picture
(In international radio communication) a code word for the letter x [n -S]
to photograph (part of the body, etc) using X-rays