Some form of vote. And this isn't an argument on which system is better or not, just a definition of democracy compared to other forms of government.

People do vote in China. You know that, right? Xi is not elected directly by popular vote but is essentially voted on by politicians who were voted in, something closer to a parliamentary style organization rather than the US system. If Xi was unpopular, the people could vote out the people supporting him in favor of challengers who support someone else for President.