Far-out has two different meaning...though one could argue they are related.
1. strange, futuristic, unusual
Example:
a)Do you think people can actually live on Mars?
b)Hmmm, I don't know, but it sure is a far-out idea.
2. excellent, cool (slang)
Example:
a)Check out my brand new car. It's a hybrid. It runs on gas and electricity and gives me a great mileage.
b)Wow, that's far-out man!