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

  • noun One that is uncontrolled and therefore poses danger.

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

  • noun nautical a cannon that breaks loose during battle or a storm and causes serious damage to the ship and its crew
  • noun idiomatic, by extension an uncontrolled or unpredictable person who causes damage to their own faction, political party etc.
  • verb idiomatic To behave in a way such as to cause damage to ones own faction, political party etc.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun a person who is expected to perform a particular task but who is out of control and dangerous


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

[From the threat posed by loose cannon rolling about a warship under sail.]


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  • whoops!

    September 20, 2008

  • These are not really at all fun to be around... Though I like the idea of calling a person this.

    September 20, 2008

  • Have you been chased by a loose cannon in your day, c_b?

    September 20, 2008

  • Is a loose canon like a drunk monk?

    September 20, 2008

  • Thankfully not, reesetee--at least not a *really* loose one. One of the pins came out of the... I wish I knew the name for the metal plate that holds the cannon onto the gun carriage... Anyway those things jump like hell if they're not strapped down.

    But I think "loose cannon" didn't refer to this kind of mishap, but to the kind of large cannons used on navy ships, gunships, that used ropes to keep them in place so they didn't roll all over the deck and crush people. It wasn't just the ordinary recoil or malfunction of the gun or hardware that made a loose cannon, but the failure of the ropes. I can't imagine being near one of these machines if it were *really* loose. It's truly deadly. And makes the phrase, in reference to a person who's uncontrollable to the point of being dangerous, really a powerful saying.

    P.S. Asativum... HEE!! :)

    September 20, 2008

  • The metal plate that anchors the cannon to the gun carriage is called a trunnion cap. The big "pin"-like protuberances on either side of the barrel, which the cap is locked on top of, are the trunnions. *whew*

    September 21, 2008

  • Zoiks! Thanks, c_b. I found out about the literal meaning behind "loose cannon" when I started my "Three Sheets to the Wind" list. Sounds terrifying, to be sure. At least you were on land when the trunnions came out of the trunnion cap (is that right)?

    September 21, 2008

  • I was on land, and so was the gun, which is actually a really small one (3- or 6-pound shot vs. 18- or 24-pounders on warships or siege lines). And the trunnion itself didn't actually bust loose. Only one trunnion cap key was not fully locked in, and the force of a normal firing was enough that the barrel jumped a bit, jostling the key out and lifting the trunnion cap some. No harm done, but it's a sobering experience to realize what could've happened—and what must have happened (at least on occasion) in the past when these things were in common use.

    September 21, 2008

  • See 15th secure your guns (and its list) for more info.

    October 10, 2008