a unit used to express the effects of acceleration or deceleration on the human body. One stapp represents an acceleration of 1 for a period of 1 second, or 9.80665 meters per second per second for 1 second. The unit is named for the U.S. Air Force physician John P. Stapp (1910-1999), a pioneer in research on the human effects of acceleration during the 1940s and 1950s.