1. loose cannon - Noun
2. loose cannon - Verb
3. loose cannon - Phrase
a person who is expected to perform a particular task but who is out of control and dangerous
Source: WordNetThat was Hera. Her Majesty, the Loose Cannon. Rick Riordan
The regional security in the Middle East cannot be further compromised by an Iranian loose cannon. Russ Carnahan
Courtney Love is a loose cannon. She says what she thinks. She's wild on the red carpet. You get the best sound bites from Courtney Love. Steven Cojocaru
I'm politically inclined towards the left, but I don't like to be in anyone's gang; I'm a bit of a loose cannon. Joanne Harris
I don't think I'm made of the right stuff to be a politician. I think I'm made to be a loose cannon. Penn Jillette