Yelling “Hey bitch, get over here!” to your dog that happens to be female…
Screaming “You suck” at a vacuum cleaner…
The OP is a complete gorm.
You have a derth of a bad qualities.
I know this black guy that can best be described as niggardly but I think that is just because he grew up poor.
Okay, you made me look.
I couldn’t find anything except for this and that would mean I am either brainless or a skinny person that lives in the mountains. Dictionary.com says that it’s a Variant of gaum which means “to smudge or smear,” which only confuses me.
Wait, but then I found this:
So I figure either you came up with a nice obscure compliment that sounds vaguley insulting in the spirit of the thread or you’re a big meanie. 
I hope all your children are born naked.
“My dick is bigger than yours” … spoken to a woman.
Maybe she’ll reply, “What twattle!”
"That’s an oxy…
moron!
I just want to let you know, in confidence, that the OP is an admitted thespian…
Kiss my ass!
Please?
Semprini!
The aftershave of course…
And also: “Death by Snu-Snu!”
Yep gormless is careless and stupid, so being a gorm can’t be too bad.
Maybe you have an over inflated sense of humility.
You’re very good at this…
Puck my stick, ya fathermuckin’ corksocker!