“Hang loose” is what you tell someone who needs to chill out and let the waves carry them away from their problems man. Align your chakras with the Earth and so on.

Seriously though, the reason I wrote like that is I’m using the slang of roughly 90s/2000s-ish California surfer culture, which is where the hand signal was used to tell people to relax and be happy. Or say hi and let them know you are relaxed and happy.