human chorionic gonadotropinn. Abbr. HCG A hormone produced by the placenta that maintains the corpus luteum during pregnancy.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.hu?man chorion?ic gonadotro?pin n. 1. a gonadotropic hormone that stimulates the production of estrogen and progesterone: its presence in blood or urine is an indication of pregnancy. 2. a commercial form of this substance, used in the treatment of testicular or ovarian disorders. Abbr.: hCG Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.