Definition of trunnion in English:

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Pronunciation: /ˈtrənyən/


1A pin or pivot forming one of a pair on which something is supported.
Example sentences
  • The introduction of trunnions, the pivots in the middle of the barrel permitting it to move independently of the carriage, was a simple but important development.
  • The main frame of this machine is fitted at its base with trunnions, which work in a foundation plate.
  • Although the compass carries no maker's marks, it is designed to fit across the transit's trunnions and has a pin that fits a hole on the transit.
1.1A supporting cylindrical projection on each side of a cannon or mortar.
Example sentences
  • The gun is fitted with a trunnion mounted telescopic sight for direct firing up to 3,000m.
  • As with the machine-gun platform, the turntable and trunnions are intact, but the gun itself is missing.
  • The barrel and breech have been salvaged, so all that remains at the top are a pair of trunnions.


Early 17th century: from French trognon 'core, tree trunk', of unknown origin.

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