skull-crusher n. a weight-lifting exercise in which one lies face upward on a bench and uses the arms to extend barbells above the face and head. (source: Double-Tongued Dictionary)
Further reading
In 1968, students at Cheyenne High School in Cheyenne, Wyoming, compiled a collection of their own slang, including the word Clyde, used to refer to one’s head, as in Use your Clyde! This is part of a complete episode.
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