What does "breech closer" mean?

a metal block in breech-loading firearms that is withdrawn to insert a cartridge and replaced to close the breech before firing

What is a synonym for "breech closer"?

Common synonyms include: breechblock.

Rare ·Advanced level

Noun

1
a metal block in breech-loading firearms that is withdrawn to insert a cartridge and replaced to close the breech before firing wordnet