I've been dying to get behind the wheel of this big boy.
{i} restaurant chain in the United States; type of steam locomotive divided into segments (has a 4-wheeled front truck, one section of 8 driving wheels, another section of 8 driving wheels and a 4-wheeled truck in the back)
{i} large boy, boy of great size; big gun, person or company having predominant status in a field, person with distinguished prevalent power in a specific field