- a vertical pin attached to some axles to serve as the axis for a wheel spindle, so that the wheel may be turned for steering
- the headpin or the center pin in bowling, tenpins, etc.
- Informal the main or essential person or thing
- (motorized vehicles) The axis around which steered wheels pivot; a bolt that holds the axis in place—a kingbolt.
- (ten pin bowling) The pin at the centre of the triangle of bowling pins (originally the tallest pin in kayles). Sometimes also the headpin at the apex.
- The most important person in an undertaking or organization.
- The bolt holding together the truck of a roller skate or skateboard.