the GNU version of the Collaborative International Dictionary of English
n. The mechanism for closing the breech of a breech-loading firearm, in artillery consisting principally of the breechblock, obturator, and carrier ring.
The Century Dictionary and Cyclopedia
n. A mechanism for closing the bore or chamber of a breech-loading small-arm or cannon; a breech-closing apparatus.
Word Usage
"Hier encore, un journal américain annonçait la fermeture de ses rotatives pour passer uniquement à la version online du quotidien."