Breechblock
Breech´block
| n. | 1. | The movable piece which closes the breech of a breech-loading firearm, and resists the backward force of the discharge. It is withdrawn for the insertion of a cartridge, and closed again before the gun is fired. |
| Noun | 1. |  breechblock - a metal block in breech-loading firearms that is withdrawn to insert a cartridge and replaced to close the breech before firingSynonyms: breech closer |