Steamfunk can be defined as a subgenre of SF/Fantasy that is aligned with Steampunk. Like Steampunk, Steamfunk resides in an imaginative alternative world in which electricity does not exist; machinery is powered by steam and (sometimes) gas, such as with gas streetlights. And the heroes are African American, and all the social ramifications of that are very real. Some alternate history about the Civil War is one of my favorite themes.
Of course, as anyone whose ever read it will tell you, the above is a bare bones definition. Steamfunk is full of marvelous creations…of steam-powered robots, fantastical flying machines and worlds separated by layers of technology and class, all of which are wild and weird and take some getting used to (for me), but were well worth the effort.