contrast medium: Meaning and Definition of

con'trast me"dium

Pronunciation: [key]
— Med. Med.
  1. a radiopaque substance injected into a part of the body, as the stomach or duodenum, to provide a contrasting background for the tissues in an x-ray or fluoroscopic examination.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.