loose cannon

loose cannon

Someone who has the propensity to act unpredictably or to lose their temper very quickly. You really have to be mindful of what you say to Jake. He's a loose cannon, and the smallest things will send him into a fit of rage. The star quarterback's reputation as a loose cannon hurt his chances of being signed by a new team.
See also: cannon, loose
Farlex Dictionary of Idioms.

loose cannon

a person whose actions are unpredictable and uncontrollable. As it turned out, he's not just a loose cannon. He makes sense. Some loose cannon in the State Department has been leaking stories to the press.
See also: cannon, loose
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

loose cannon

One who is uncontrolled and therefore a serious and unpredictable danger. For example, We can't trust her to talk to the press-she's a loose cannon. This metaphoric expression alludes to cannon mounted on the deck of a sailing ship, which if dislodged during combat or a storm could cause serious damage to both vessel and crew by sliding about. Its figurative use dates from the first half of the 1900s.
See also: cannon, loose
The American Heritage® Dictionary of Idioms by Christine Ammer.

a loose cannon

COMMON If you call someone a loose cannon, you mean that their behaviour is unpredictable and could cause problems. He was also getting a reputation for being a loose cannon; an accident waiting to happen. Thomson can be a loose cannon — he's not easy to control. Note: This expression refers to the cannons which used to be carried on the decks of warships. If one of the cannons was not properly fastened down, it could spin round and make a hole in the ship.
See also: cannon, loose
Collins COBUILD Idioms Dictionary, 3rd ed.

a loose cannon

a unpredictable person or thing likely to cause unintentional damage.
A loose cannon was originally a cannon that had broken loose from its fastening or mounting, an accident especially dangerous on wooden ships of war.
See also: cannon, loose
Farlex Partner Idioms Dictionary

a ˌloose ˈcannon

(disapproving) a person who behaves in a way that you cannot predict, often with serious or damaging results: He has a reputation as a loose cannon whose comments sometimes upset Wall Street.On a ship, a cannon that was not properly tied down was a danger as it could roll around and hurt people or damage the ship.
See also: cannon, loose
Farlex Partner Idioms Dictionary

loose cannon

n. a loudmouth; a braggart. As it turned out, he’s not just a loose cannon. He makes sense.
See also: cannon, loose
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions

loose cannon, a

A grave and unpredictable hazard. This term comes from the days of sailing ships, when cannon—guns for firing heavy projectiles—were mounted on deck. If during combat or a storm a cannon came loose from its mounting and rolled about the deck, it could severely damage the hull, causing the ship to sink, as well as injure the crew. In the twentieth century the expression began to be used figuratively for a person who behaves unpredictably and is potentially damaging, as in “The president’s secretary was a loose cannon—she couldn’t keep these matters confidential.”
See also: loose
The Dictionary of Clichés by Christine Ammer
See also:
  • a loose cannon
  • loose cannon, a
  • fly into a temper
  • beware of
  • beware of (someone or something)
  • blow (one's) cool
  • blow cool
  • blow one’s cool
  • blow one's cool
  • blow your cool
References in periodicals archive
A check on the Government's Companies House website confirms that Loose Cannon Event Management was dissolved on November 8, 2016.
"While we understand the concerns and frustrations of concertgoers, this matter is now closed." Loose Cannon has been responsible for a number of high-profile events in the North East, including Snoop Dogg and Olly Murs concerts.
Go to sales@boxfroguk.com loose cannon the problem no-one in PR him.
Yet she says the chances of some form of recompense are "increasingly unlikely" due to the "disappearance" of Loose Cannon.
Volume I in a New Series: Selected Salvos from the Loose Cannon Libertarian by Garry Reed, Libertarian Opinionizer
"He (Blatter) is a bit of a loose cannon," said Brady.
That's tough enough to achieve without a loose cannon like Kadafi flapping his gums.
Were I to write that book today I would call it The Biggest Loose Cannon in America and leave off the question mark.
"I'd hear 'Loose cannon.' I don't think speaking honestly on any of the issues should characterize you as a loose cannon."
One of the new elected Dover board members, Judy McIlvaine, called Robertson's comments "unbelievable." Mcllvaine told the Philadelphia Inquirer, "He's such a loose cannon. Perhaps it's an honor that we have attracted the ire of Pat Robertson."
Historic parallels always pose difficulties, but Ahmadinejad is clearly a loose cannon and an embarrassment.
As he is in any band, Valente is the loose cannon, for although he blends well in the section his sound in a solo is almost overwhelming, certainly against this polite rhythm team.
The Speaker of the House viewed him as something of a loose cannon, but also as someone who could be useful if he could be held in check.
ACTION man Stephen Seagal plays a loose cannon copper on the trail of all manner of nastiness and corruption in Detroit.
A loose cannon who delights in attacking environmentalists in coarse language, the oil state congressman is a prime House author of "takings" legislation designed to protect property owners from the enforcement of environmental laws.