Wave is an emote in Fortnite Battle Royale game, that has a simple set of dance moves.
The player will only swing his left hand.
How to get
It is a free path tier 5 Battle Pass reward. Try to reach Level 5 in Season 2 to unlock it!
Because that prize is on that process, you do not need to purchase the Battle Pass to open it up.
Nevertheless, you can buy to advance faster.