In the US, it is an expression that is used almost exclusively in politics to describe a politician that takes inconsistent positions on an issue or set of issues. It is used to paint a politician as untrustworthy on an issue or in general. I have never heard it used outside of a political discussion.
"I don't like him because he flip flops on every issue, he has no core values"
"She flip flopped on the war"
"They flip flopped on abortion"