An outgrowth or enlargement, especially an abnormal one, such as a wart.
A usually unwanted or unnecessary accretion: "Independent agencies were an excrescence on the Constitution” ( Los Angeles Times).
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.