When three guys who have hooked up with the same girl all high five.
1. They must have been friends before they hooked up with the girl.
2. Anytime two members initiate the high five the third is obligated to join.
Matt: Did you see Bradley went home with Sarah last night?
Kevin: Yeah I heard dude, Triple high five!
Bradley: Ugh... you two are douches
"They all high five"
While the common "High Five" features two people, and their hands, slapping together, the "Triple High Five" features three people slapping their hands together. This causes some issues, as the slapping sound is muted, if not completely obliterated, as the three hands coming together form a triangle. It is generally considered to be an impossible feat.
"Dudes, high five!"
"But there are three of us!"
"Then we'll Triple High Five!"