Hawaiian locals use the "shaka" to convey what locals in Hawai'i call the "Aloha Spirit," a gesture of friendship and understanding between the various ethnic cultures that reside within Hawai'i, and thus it does not have a direct semantic to literal translation. Depending on context it can also be used to communicate notions such as "all right," "cool," "smooth," and the like. (Source Wikipedia)
The origin of this hand gesture is very interesting. Read about how it started and more HERE
This Hawaiian native can assure you that the information is very accurate. (Y)
Thanks Maui for all that interesting info