Sentence:  Burkhardt was a legendary figure in the sideshow world, a mentor and instructor to a new generation of <WSD>blockheads</WSD> and other working acts who now train in private classes at Coney Island USA's Sideshow School with Burkhardt's disciple Todd Robbins (Zigun 2006). 
Meaning of the word marked with <WSD> tags:  A sideshow performer who hammers nails or similar items through his or her nostril into the nasal cavity; human blockhead.