Complete The “The Legendary Beast” Quest-

Once you have completed A Visitor From Another World, talk to the Serious Handler and initiate this quest from the Quest Board. Upon arriving to Elder's Recess, you will be shown the introductory cutscene of the Behemoth and then you'll be able to fire an SOS flare.
This is a very challenging monster so make sure to prepare by visiting the Behemoth page. You only need to damage it until the Behemoth runs away (after summoning a rather deadly comet!)
When you return to Astera, talk to the Serious Handler to trigger a cutscene and obtain the gesture "Final Fantasy XIV Jump".
Talk to the Serious Handler again after the cutscene for a Behemoth quest: He Taketh It with His Eyes.
If you unlocked Seliana the Serious Handler can also spawn there instead of Astera.
The quest is not available when you're with the Serious Handler during the Iceborne story.

The Dragoon Jump was designed to dodge the Behemoth's Meteor Attack, in the FF series, the Dragoon's Jump is also used to dodge otherwise, dangerous/lethal attacks. This gesture and it's effect against the Behemoth's Meteor is intended.

SOURCES SITED:
https://game8.co/games/Monster-Hunter-World/archives/315190
https://monsterhunterworld.wiki.fextralife.com/The+Legendary+Beast
(TIPS ON HOW TO USE THE GESTURE TO AVOID THE BEHEMOTH ECLIPTIC METEOR SOURCE : https://gamefaqs.gamespot.com/boards/211368-monster-hunter-world/76875423)
Video showing the Jump through Behemoth Meteor for timing reference - https://www.youtube.com/watch?v=4lFUI8LplIE&t=11s


REWARDS: 17640 zenny
Gesture: Final Fantasy XIV Jump