Someone who is xenophobic is abnormally hostile toward foreigners. If you don't want any foreign people in your town, then you're xenophobic.
Xenophobic comes from the Greek and literally means "fear of strangers," although when we talk about someone who is xenophobic, we're talking about someone who has converted fear into hatred or contempt. Sometimes people who discriminate against foreigners or feel very strongly that no one should be allowed to immigrate to their country are also called xenophobic.