the Yellowstone National ParkYel·low·stone Na·tion·al Park, the /ˌjeləʊstəʊn ˌnæʃənəl ˈpɑːk $ -ˈpɑːrk/ a large national park mostly in Wyoming, in the northwestern US, known for its hot springs and geysers (=natural springs of hot water that rise suddenly into the air), especially one called Old Faithful which many tourists come to see