Pinhead: n. 1. The head of a pin. 2. Anything small, trifling, or insignificant. 3. Slang. A stupid person. 4. Theology. A preferred angelic dance spot. cf "How many angels can dance on the head of a pin?" 5. Medicine. Popular/vulgar term for person with Microcephaly, an abnormally small head due to failure of brain growth. 6. Popular culture. a. A fannish name for an anonymous character in the Hellraiser films; b. A comic strip character, see Zippy the Pinhead