[{"Bold_text": "noun", "List Items": ["Bowling. headpin .the pin the center; the number five pin .", "headpin .", "the pin the center; the number five pin .", "Informal.the person of chief importance in a corporation, movement, undertaking, etc.", "Informal.the chief element of any system, plan, or the like.", "a kingbolt.", "either of the pins that are a part of the mechanism for turning the front wheels in some automotive steering systems."]}]