Xenophobic
It comes from the Greek words ξένος (xenos), meaning "stranger," "foreigner," and φόβος (phobos), meaning "fear." The term is typically used to describe a fear or dislike of foreigners or of people significantly different from oneself, usually in the context of visibly differentiated minorities.
General
A political poster of the far right National Democratic Party of Germany.
According to the Oxford English Dictionary (OED), the word xenophobia consists of two parts: xeno, a combining form meaning "guest, stranger, person that looks different from you, foreigner", and phobia, "fear, horror, or aversion esp if… morbid…". It is more broadly defined in the Dictionary of Psychology "a fear of strangers".
As defined by the OED it can mean a fear of or aversion to, not only persons from other countries, but other cultures, subcultures, subsets of belief systems; in short, anyone who meets any list of criteria about their origin, religion, personal beliefs, habits, language, orientations, or any other criteria. While some will state that the "target" group is a set of persons not accepted by the society, in reality only the phobic person need hold the belief that the target group is not, or should not be, accepted by society.
While the phobic person is aware of the aversion, even hatred, of the target group they may not identify it or accept it as a fear.
As with all phobias, a xenophobic person, or a xenophobic is aware of the fear, and therefore has to genuinely think or believe at some level that the target is in fact a foreigner. This arguably separates xenophobia from racism and ordinary prejudice in that someone of a different race does not necessarily have to be of a different nationality.
In various contexts, the terms "xenophobia" and "racism" seem to be used interchangeably, though they can have wholly different meanings (xenophobia can be based on various aspects, racism being based solely on race and ancestry).
For xenophobia there are two main objects of the phobia. The first is a population group present within a society that is not considered part of that society.
Often they are recent immigrants, but xenophobia may be directed against a group which has been present for centuries. This form of xenophobia can elicit or facilitate hostile and violent reactions, such as mass expulsion of immigrants, pogroms, or in the worst case, genocide.
The second form of xenophobia is primarily cultural, and the objects of the phobia are cultural elements which are considered alien.
All cultures are subject to external influences, but cultural xenophobia is often narrowly directed, for instance at foreign loan words in a national language.