What is knucklehead?

Knucklehead is a slang term used to describe a person who is foolish or stupid. It can also refer to a type of Harley-Davidson motorcycle, specifically the model that was produced from 1936 to 1947. The name "knucklehead" comes from the distinctive shape of the rocker box, which resembles a clenched fist with the knuckles protruding. These motorcycles were known for their high performance and reliability, and are considered highly collectible by enthusiasts today.