A technique where chakra concentrated between chest and mouth is converted into fire and expelled from the mouth either as a massive orb of roaring flame or as a continuous flame-thrower. The scope of the attack is altered by controlling the volume of chakra that is mustered. The released flames will engulf their target, and leave a crater on the ground's surface. This technique apparently requires more than average chakra reserves and most genin should not be able to do this technique.
The Uchiha clan also uses this technique as a "coming of age" rite, using it to test wether a young Uchiha is fully matured or not, and as such was a common and one of the more favoured technique amongst them.
According to Kakashi Hatake, this technique was originally created by the Uchiha clan, becoming one of their favoured moves at which they became very adept.
In Naruto Shippūden: Ultimate Ninja 4, after learning all other techniques and beating Kakashi in battle, he will teach the player this technique and allows the player to customise it to characters in free battle.
In Naruto Shippūden: Ultimate Ninja 5, during The Chambers of the Darkness: The White Chapter, you get a scroll with this technique in the last room of Orochimaru's Hideout.
During his battle with Kakashi, Naruto, Sakura and Chiyo, Itachi was seen using the hand seals: Boar, Horse, and Tiger to create this technique.