Probably one of the most popular
words to come out of Avatar: The Last Airbender, it translates to "fire meeting."
Agni Kai's are a popular
(and violent) way of settling arguments in the Fire Nation. One person challenges another
and they both face off in a fire-bending battle.
This was also
one of the events that led of up to the banishment of Prince Zuko in the series. It also
his mentally unstable sister, Princess Azula.