A raised hand, with the fingers separated between the ring finger and the middle finger.
This gesture was invented by one of the characters of?Star Trek series characters, the?Alien. There, it meant the formal greeting and wished to prosper of his race.
The series' fans use it precisely in the same meaning — mostly, instead of "hello" or "goodbye" to a friend. Yet, it is already not only a geek-only gesture, and it is used in this sense not only by fans but even by those who have never seen Star Trek.
Vulcan Salute was approved as part of Unicode 7.0 in 2014 under the name “Raised Hand with Part Between Middle and Ring Fingers” and added to Emoji 1.0 in 2015.
U+1F596
? Raised hand with part between middle and ring fingers