Wiktionary
n. A form of firearm action where the sealing of the breech is done with a specially shaped breechblock able to rotate on a pin.
Wikipedia
A rolling block is a form of firearm action where the sealing of the breech is done with a specially shaped breechblock able to rotate on a pin. The breechblock is shaped like a section of a circle. The breechblock is locked into place by the hammer, thus preventing the cartridge from moving backwards at the moment of firing. By cocking the hammer, the breechblock can be rotated freely to reload the weapon.
Usage examples of "rolling block".
One would be the standard infantry rifle and would be based on the rolling block design.
It was a driving, rolling block coming in from the blind side, and the impact was impressive.
I dived into them with a rolling block, barreling into their legs, knocking several of them down.
Biff bolted across the room, putting a rolling block on two of the collegians.