An underground starter house in Minecraft is a cozy, hidden base built beneath the surface. It typically features a compact but functional layout with essentials like a crafting table, furnace, chest storage, and a bed. Using natural materials like wood and stone, it blends seamlessly with the environment. Often, a glass ceiling or a few skylights provide natural light, while torches or lanterns illuminate the interior. Accessible by a ladder or staircase, it offers a safe, concealed space perfect for early survival gameplay.