Plead guilty or confess to a crime in exchange for a lighter sentence; also, plead guilty to a lesser charge in exchange for not being tried for a more serious charge. For example, Arnold decided he was better off copping a plea than facing a jury. [Colloquial; 1920s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.