a 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

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

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

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
References in periodicals archive ?
On the pitch he's a great player that every coach would want in his team, but off it he's a loose cannon.
Inevitably critics will dismiss Ms Short as a loose cannon with her own agenda.
He (Blatter) is a bit of a loose cannon, He's an embarrassment to FIFA.
Mcllvaine told the Philadelphia Inquirer, "He's such a loose cannon.
So what if Odalis Perez is something of a loose cannon who tends to alienate a teammate every time he opens his mouth or cranks up the volume on the clubhouse stereo system?
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.
Though a very sweet dog, a spotty discipline regimen has turned Sid into a bit of a loose cannon in the behavior department.
John to me is known as a loose cannon, something I was like all my life,' he said.
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.
Hussein was a loose cannon, but he was considered a loose cannon that could be brought under control with cautious diplomacy and economic blandishments.
If Mundie's remark was just the mental equivalent of a loose cannon on the deck of the Microsoft ship of state, we could suggest pushing the cannon overboard.
I am really sick of people who, out of ignorance or stupidity or fear, criticize Larry for being a loose cannon.
A loose cannon, Fields and his redneck friends believe America is being ``invaded'' and if they don't act soon, they will be forced to eat ``beans and tortillas'' for the rest of their lives
Last year he published his memoirs in a book called A Loose Cannon, which detailed his struggle with the world of finance.