[{"Bold_text": "noun", "List Items": ["a highway, as in a mountainous area, having many hairpin curves.", "Railroads.a zigzag track arrangement for climbing a steep grade.", "British. roller coaster roller coaster."]}, {"Bold_text": "verb (used without object)", "List Items": ["(of a road, railroad track, etc.) to progress through a series of hairpin curves; zigzag:The road switchbacks up the mountain."]}]