Trunnion /(?)/

Trun·nion

Trunnion

n.
  1. A cylindrical projection on each side of a piece, whether gun, mortar, or howitzer, serving to support it on the cheeks of the carriage. See Illust. of Cannon. (Gun.)
  2. A gudgeon on each side of an oscillating steam cylinder, to support it. It is usually tubular, to convey steam. (Steam Engine)

Phrases & Compounds
Trunnion plate
a plate in the carriage of a gun, mortar, or howitzer, which covers the upper part of the cheek, and forms a bearing under the trunnion.
Trunnion ring
a ring on a cannon next before the trunnions.