You're an assessment.

Get it? British: arse, American: ass?
You're an arse (how British people pronounce ass) ass ment.
Please tell me you got it, it's an insult.
The person is dumb if he/she doesn't understand it.
No need to explain it, let them figure it out.
Okay, I just ruined the insult. I really am Awkward.
Buh bye! Stay awesome, dudes :)