"Geez" or "Jeez" is a mild way of saying "Jesus!" It's used in other countries as well as the US.

http://www.thefreedictionary.com/geez "Used to express mild surprise, delight, dissatisfaction, or annoyance"

I agree with Peachey

ok. thanks Ian :)

He means that your question should read: What does "geez" mean? Is it US slang? However, he is also rude and unhelpful. Yes - it is a mild form of "Jesus!"