A person with a disability who reinforces the stereotype that people with disabilities don't care about their appearance and don't care what others think often at the detriment to themselves and others with disabilities.
Did you see that loosecannon at the hearing? They need to get it together!
A person, often holding a position of significant responsibility within military, political, or business contexts whose words or actions are considered by some to undermine established objectives of the greater organization.
In our operations handbook, the section with the heading "definitive loosecannon" contains a picture of John Bolton.