According to chapter 16 of Hillier et al. "Fundamentals of Corporate Finance" (3rd ed., 2017) (here is a link to a slightly different edition), instead of paying a cash dividend a company could issue new shares to the existing owners. That is called a stock dividend.
Another type of dividend is paid out in shares of equity. This type of dividend is called a share or stock dividend. A stock dividend is not a true dividend, because it is not paid in cash. The effect of a stock dividend is to increase the number of shares that each owner holds. Because there are more shares outstanding, each is simply worth less.
I do not see how this could be considered a form of dividend. There is no cash involved, just a stock split. (A counterexample would be share buyback. I can see why this is a form of dividend, because investors can cash out some of their stocks.)