loose cannon
In real, traceable use. Part of the curated seed collection; community review is coming.
Meaning · English
A person who is uncontrollable and unpredictable but likely to cause damage to the group of which they are a member.
Where it’s used:
Used
Widespread English
Sources & notes
Imported from Wikipedia “English-language idioms” (CC BY-SA 4.0, retrieved 2026-07-29), pending review.
Common questions
What does “loose cannon” mean?
A person who is uncontrollable and unpredictable but likely to cause damage to the group of which they are a member.
Is “loose cannon” formal or informal?
No register label has been reviewed yet — treat it as neutral and check the usage notes above.