Terran salute
The Terran salute was an often-required gesture of respect to fellow and superior officers (especially the captain) in the mirror universe. 

During the 2150s, it began with the right fist pressed against the left side of the chest, and then extended straight out parallel to the ground. ()

By the 2260s, the right arm was used, and the palm was opened as the arm was extended, giving it the appearance of a more traditional Nazi salute. It also resembled the salute used by the Roman Empire in Earth's ancient history. The salute was occasionally accompanied with the phrase "Long live the Empire!". The salute ceased to be used when the Terran Empire fell. (; , et al.)
Mirror universe
Communication