The most important or powerful person in a group, organization, business, or movement (e.g., the boss, leader, etc.). Primarily heard in US, South Africa. I think it sounds like a great idea, but you'll have to ask the big kahuna first.
n. the important person; the knowledgeable authority on some matter. (From the Hawai'ian word for “priest.” Sometimes capitalized.) Joe is the big kahuna around here when it comes to predicting stock market prices.