[A timely repeat from February 13, 2014] My brother-in-law’s favorite word to describe those of questionable intelligence is “knucklehead.” I like it as well. According to the Merriam-Webster Dictionary, the term “knucklehead” was first used in 1942 by ventriloquist Paul Winchell for his dummy “Knucklehead Smiff.” The word was adopted to describe a “stupid person.” There are dozens of synonyms for the word. And there are millions of people who fit the description.
The word “knucklehead” is the name of a Canadian punk rock band. It is the title of a 2010 movie and a 1975 song by Grover Washington. It is the name of an indoor amusement park in the Wisconsin Dells and a bar in Kansas City. The word is not derogatory as to race, religion, gender, ethnicity, culture or sexual orientation. It is an equal opportunity descriptor for a really stupid person.
I frankly can see limitless application for using this word. In fact it can probably best be used for anyone who disagrees with me on any given topic.
Renaissance Hombre 
Greetings…I see we have a new format for reply. Yes,a term aptly evident for application in D C
Here’s another….When I served in Brooklyn at LMC the local Norse used a term to fondly describe THEMSELVES….”SQUARE-HEAD” I got over the shock of hearing it but never
used it as an Irish-Sweed. In South Dakota such a term, especially if applied to others, would likely result in a punch in the chops…minimally.