[{"Bold_text": "noun", "List Items": ["the foremost division or the front part of an army; advance guard; van.", "the forefront in any movement, field, activity, or the like.", "the leaders of any intellectual or political movement.", "(initial capital letter)Rocketry.a U.S. three-stage, satellite-launching rocket, the first two stages powered by liquid-propellant engines and the third by a solid-propellant engine."]}]