If something is outlandish it's bizarre or unfamiliar, far outside the boundaries of expected or normal behavior. Driving around the city in a golf cart and eating spaghetti with pineapple sauce are both examples of outlandish behavior.
It's easy to imagine how the word outlandish originated. The Old English root is utland, which literally means "out-land," or foreign. Now, it would be inappropriate to refer to a foreigner as outlandish, unless, say, he shows up to the office in a red patent-leather Speedo and a ten-gallon hat.