Yes, you can undo a wave sent on Messenger. Sometimes, we might send someone a wave mistakenly. So, we need an option to undo this activity.
Just go to your friend’s inbox whom you send a wave mistakenly.
Then press and hold the wave icon.
Then you should find the remove option. Here you will find two sub-options: Remove for me and Remove for everyone. Press on Remove for everyone. Then, your wave will be unsent.