(rhymes with aristocracy) A noun, denoting a form of government run by the worst people – the meanest, the basest, the most cowardly people. A neologism, formed from κάκιστος, meaning “the worst [in a variety of senses]” and κρατέω, meaning “to govern, to rule over, to have or gain mastery over.”
It mirrors ‘aristocracy,’ which would have originally denoted government by the best people; through the influence of classism, the ‘best’ people were assumed to be those of the owning class, and thus the word came to have its current meaning. Kakistocracy, being a new word, will presumably undergo a semantic metamorphosis in a different direction. Many people, for instance, might argue that our government is in fact run by the meanest, basest, most cowardly people: politicians. A member of a kakistocracy is, obviously, a kakistocrat.
Note: this word appears in the Urban Dictionary attributed to Bryan H of Simi Valley, CA on Jun 18, 2005; my independent coinage of it dates to around Mar 20, 2000.