intrauterine device (IUD), variously shaped birth control device, usually of plastic, which is inserted into the uterus by a physician. The IUD may contain copper or levonorgestrel, a progestin (a hormone with progesteronelike effects; see progesterone). Apparently the IUD creates a hostile environment for the fertilized egg.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.