Shaka wave

Hold your hand in front of you, palm facing away from you.
Curl down the three middle fingers while holding out your thumb and pinkie finger. 
Then shake the hand back and forth.   Palm can also be turned inward and shaken.
*  just read that the back of the hand faces the recipient, the other way is called the "tourist shaka"!   Well, well  . . . .

It's a sign of brotherhood and everything OK, let it all hang loose.   At the end of our TV newscasts, the camera person always shows some locals/tourists doing the shaka and smiling for the camera.  This wave has gotten the idea.
Here's some background.