breechblock definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
the block in a breech-loading gun which when closed receives the force of the combustion of the charge
breechblock definition by American Heritage Dictionary
The metal part that closes the breech end of the barrel of a breechloading gun and that is removed to insert a cartridge and replaced before firing.