Any foreign country whose internal or external politics your personal superpower (like, say, the US) does not agree with.

The word is used to whip into a frenzy the bloodthirsty masses of justifiedly enraged citizen/voters, so that the subsequent carpet bombing of said rogue state does not come as a surprise: rather, a natural consequence of the state of things.

The words "rogue state" indicate clearly that foreign policy is spinning into motion: that's why they are rarely heard in countries that, like Italy have no foreign policy (and, for the matter, few policies) at all.

Today marked the end of the use of the term rogue state as the official United States description for countries that are "disruptive."

On 6 18 00 on NPR, and again today in an article in the Washington Post, Madeleine Albright, Secretary of State, for the United States, states that this term is no longer going to be used.
Her spokesman, Richard Boucher says that "states of concern" is the term that will be used in it's place.

There is NO truth to the rumor that next year the term will changed to places that just better quit it, if they know what's good for them.