Sorry to have to answer your question with No ...it is definitely not a cannonball. The characteristics of the damage on it indicate is is made of clay -- not stone. There absolutely never were any clay cannonballs, because the cannon's explosive firing-blast causes clay to shatter into small pieces.
Waaay back at the very start of cannon history (in China and Medieval Europe), there were a few stone cannonballs. But yur ball is definitely not made of stone. I would agree with ABruce that it is "most likely" an antique clay ball from a lawn-game. I can't recall its name, but I've seen video of an ancient lawn-game (but still being played today) in which players roll a Softball-sized clay ball across the lawn to knock other balls out of the game. But of course, your white clay ball may be some other kind of ball. I am 100%-certain it is not a cannonball. Sorry I don't have happier news for you.