from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun A pin or gudgeon, especially either of two small cylindrical projections on a cannon forming an axis on which it pivots.

from The Century Dictionary.

  • noun One of the cylindrical projections on the sides of a cannon, cast or forged in one piece with the cannon itself, which support it on its carriage.
  • noun In steam-engines, a hollow gudgeon on each side of an oscillating cylinder, which supports the cylinder, and through which steam is received and exhausted.

from the GNU version of the Collaborative International Dictionary of English.

  • noun (Gun.) 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.
  • noun (Steam Engine) A gudgeon on each side of an oscillating steam cylinder, to support it. It is usually tubular, to convey steam.
  • noun (Gun.) 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.
  • noun (Gun.), [R.] a ring on a cannon next before the trunnions.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun One of the short stubby bearings on either side of a cannon; a gudgeon.
  • noun A similar rotational bearing comprising a rotating arc or ring sliding in the groove of a stationary arc, used in machinery to allow a workpiece to be moved relative to a fixed tool.


from The American Heritage® Dictionary of the English Language, 4th Edition

[French trognon, stump.]

from Wiktionary, Creative Commons Attribution/Share-Alike License

From French trognon ("core, stump").



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  • "...all the guns but three were made of painted wood and of the others two had had their trunnions beaten off, so that they could not be pointed with any sort of accuracy, while the third, an archaic brass piece, had once been spiked, and the person who bored out its touch-hole had made a sad botch of it."

    —Patrick O'Brian, The Ionian Mission, 323

    February 14, 2008

  • What a great word.

    February 14, 2008

  • Agreed.

    February 14, 2008

  • "trunnions

    Short horizontal bars on both sides of a cannon by which it is mounted to the gun-carriage and that provide the axis upon which the cannon pivots when being aimed."

    A Sea of Words: A Lexicon and Companion for Patrick O'Brian's Seafaring Tales, 436

    Whew. I figured I should really know what the heck these are.

    February 15, 2008

  • Really. I mean, if you're going to talk about someone having their trunnions beaten off, you should know what you're talking about. ;-)

    February 15, 2008

  • "TRUNNIONS, two wings projecting from the sides of a piece of ordnance, by which it is supported upon its carriage." (citation in Historical Military Terms list description)

    October 9, 2008