A pill containing a drug, especially an estrogen or estrogen substitute such as diethylstilbestrol, that prevents implantation of a fertilized ovum and is therefore effective as a contraceptive after sexual intercourse.
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.