A loose cannon is an unpredictable person: you never know what they will do next. They act on their own, say things they shouldn't and can harm their own team. Literally, it's a cannon that has broken free of its ropes: picture it rolling around the deck and smashing everything in its way. The idiom is conversational and often appears in news stories about politicians and athletes. In essays, unpredictable is used instead.
When would you say a loose cannon?
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be a (bit of a) loose cannon; a loose cannon in + team/party/company
- The company fired its spokesperson after he became a loose cannon on social media.
- Mike is a talented player, but he's a loose cannon who argues with every referee.
- Don't invite Rita to the negotiations; she's a bit of a loose cannon.
What changed
First versionThe coach dropped him from the team because he was a lose cannon.
RevisionThe coach dropped him from the team because he was a loose cannon.
Lose is the verb meaning to stop having something, but the idiom needs the adjective loose, “not fixed, free”. The two words also sound different: lose ends in a voiced [z] sound, and loose in a voiceless [s]. One letter was corrected.
Don't confuse it with a free spirit, someone who lives the way they like. That's more of a compliment: She's a free spirit who travels alone. A loose cannon is always a criticism: such a person puts everyone they work with at risk.
Your turn
Nobody knows what Dan will say at the meeting with clients. He's clever, but he's a bit of a ___.
Show the answer
loose cannon — Nobody knows what Dan will say to the clients, so he's unpredictable: a loose cannon. A wet blanket is someone who spoils other people's fun, but here the issue is risk at a business meeting.
Describe a character from a film or TV series, or a real person, who could be called a loose cannon. Say who they are and what unpredictable thing they did.
In the film, the young detective is a loose cannon: he arrests the mayor without telling his boss.
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