1. The biggest dickhead you know is likely to be a Class A DICKHEAD as they top the list of biggest dickheads of all time. Everyone thinks they are a dickhead.
2. Term used to describe people who are addicted to Class A illicit drugs such as Heroin or Crack.
3. A politician who talks bullshit (possibly all politicians)
A Chav who steals your bike is likely to be a Class A Dickhead.
A meth addict could be described as a Class A dickhead
An absolute dickhead who has performed an unbelievable act of dickheadism, therefore deserves to be called a "dickhead and a half" which is much more offensive than just saying "you're a dickhead"
12 step recovery jargon referring to someone new who talks about how great life is, now that they'resober. Usually meaning that the person is out of touch with reality.
The new guy seems pretty happy for a dude who has no job, no money and no family. He must be on a pink cloud.