Thought to be derived from someone who misheard "knucklehead," a nickel-head is someone who's got quite a few screws loose "up there." They aren't the sharpest tools in the shed. Its meaning stems from the fact that a nickel is valued at only five cents, and thus nickel-heads are a step up from their dimwitted cousins, penny-heads.
"I failed my open book quiz."
"You must be a nickel-head."
7π 3π
A homosexual who also has kids. Usually referring to a male. Works in tandem with the phrase βthree dollar billβ.
He is not just a three dollar bill, because he has kids, heβs a two headed nickel.