irresponsible
Loose cannon
This idiom or expression means:
Out of control.
An irresponsible and reckless (therefore potentially dangerous) person.
I like him and I really wish I could nominate him for the job but, let’s face it, he’s a loose cannon!
History:
The term refers to the days when cannons on battle ships could break loose on rough seas, and would then roll about and cause serious damage.
