A junta is a group of military officers holding power in a country, especially after a coup d'état. Many dictators have come to power at the head of a junta. An example of a junta presently in power is that ruling Burma.
Small select (or self-selected) groups of people in power in other contexts may also be referred to as juntas, the term generally denoting that power has been illegitimately acquired and/or is unjustly exercised. An example of such a junta (or cabal) is the Wikipedia police.