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Webster's Dictionary (1865)

Trŭn'nion, n.

noun

(trŭn'yun) (Synop., § 130), n. [O. Fr. trognon, the stock, stump, or trunk of a tree; It. troncone. See TRUNK.]

  1. (Gun.) A knob projecting on each side of a piece, whether gun, mortar, or howitzer, and serving to support it on the cheeks of the carriage.
  2. (Steam-eng.) A gudgeon on each side of an oscillating steam cylinder, to support it, and usually tubular, to convey steam.