Sentence:  Zip the What-Is-It was simply a Negro idiot. ... For half an hour at a time, David Belasco used to watch Zip at Coney Island. The producer insisted he saw signs of intelligence in the <WSD>pinhead</WSD> ... 
Meaning of the word marked with <WSD> tags:  A human head that is unusually tapered or small, often due to microcephaly, or a person with that trait. Often promoted in freak shows as "human pinheads".