Kamui

By focusing his Mangekyō Sharingan on a particular point, Kakashi can force that point to collapse in on itself, ultimately sending everything in the vicinity to another dimension. Kamui costs a large amount of chakra to perform, especially in Kakashi's case, as his body has not completely adjusted to the Sharingan. Kakashi can only manage to use this technique up to three times in a given day, even when starting at full strength. When first seen, Kakashi's aim was imperfect, with it taking two attempts to hit Deidara with the technique. By the time of Pain's attack on Konoha, however, his aim had improved, being able to focus more accurately on fast-moving objects. His improvement with the technique is also seen when he manages to warp away two arrows fired by Sasuke's Susanoo without becoming fatigued, noting them to be too fast to dodge.

Kakashi's Kamui bears some resemblance to Madara Uchiha's teleporting technique as Madara's appearance when he is warping between different dimensions is the same as the swirl pattern on his mask and when Kakashi uses Kamui, the warping of the space is the same. It is unknown if the two techniques are related, however.

Influence
Kamui is the word for a divine being in Ainu mythology, although it is almost never written with kanji in modern times. In a more generally Japanese context, kamui refers to the might and majesty of the gods, particularly the Shintō Kami.

Trivia

 * According to the Third Databook, "If one spends a lot of time and trains one's chakra over and over again, this technique can be invoked." This might hint that other Mangekyō users can access the technique, but this is not confirmed.