It’s definitely meant for outdoors. It’s extremely heavy, probably a few hundred pounds or more, Ceramic possibly, it seems more like a very old concrete mixture. The slot on the top is interesting and with the back unfinished it definitely fit into or was part of some other structure. Perhaps supporting some kind of fountain?It's commonly called a corbel. True corbels are part of and project from the structure of a building and help support the weight above. They are recognizable because of the reverse stair step design. Here a picture of some fancy ones with lions (a common theme).
Yours is an ornamental corbel. It wasn't designed to support any weight it's just a finishing piece. It's proper architectural name would be a console or sometimes they are referred to as building furniture.
Yours may be glazed ceramic or painted plaster. If it's plaster it was mounted indoors.