I don't speak Russian, but whatever the Russian word is for "book." Or maybe others called it a novel but Tolstoy rejected the label. I'm not sure.

Either way, the word "novel" wasn't necessarily equivalent to how it is used today: any book length work of narrative fiction.

Though watch out, this is a rabbit hole. Just look up novel on wikipedia. You'll see a big orange message at the top which is the first sign there is a problem. And then the article is excessively long. A lot of ink has been spilled trying to define what a "novel" is.