noun
stone-roasted sweet potato
Sweet potatoes roasted in hot stones or pebbles, a traditional Japanese street food often sold from carts.
冬になると、石焼き芋の屋台が出る。
In winter, stone-roasted sweet potato carts appear.
焼き芋 is a general term for roasted sweet potatoes, while 石焼き芋 specifically refers to those roasted in hot stones.
Compound of 石 (stone), 焼き (roasting), and 芋 (potato).