"A term from French philosophy that has several, sometimes overlapping meanings in cultural studies, including anthropology and psychoanalysis.
1 Most commonly, another person or group of people who are defined as different or even sub-human to consolidate a group's identity. For example, the Nazi's internal cohesion depended in part on how they defined themselves against (strove to maintain distinctions from) their image of the Jews. In this sense, "The other" is the devalued half of a binary opposition when it is applied to groups of people. (See binary opposition.)"
The concept of the Other centers around the assumption that in any binary, one thing is valued over another. So, in the binary "white/black" or "man/woman" or "us/them", there is a built in, subconscious assumption that one of the set is better than "the other".
So simply being a "European white male colonizing Africa" inherently assumes that you are better than the "African blacks" you are colonizing.
This term is often used as a verb, as something people do, as well, such as the act of "Othering" someone or a group. We could say that Nazis "Othered" the Jews that whites "Other" blacks when terms like "them" or "black man" (vs. "man") are used.
(Often this term is placed in "quote marks" to emphasize its technical, theoretical use.)
Compare to the opposite: Empathy
Othering one's enemies normally justifies denying them the same rights we take for granted. The most extreme form of Othering is to dehumanize the Other to the point that you no longer consider them human; commonly, these people are called "monsters" or "beasts" or, as the Nazis called the Jews, "vermin".
Cultures often "Other" behaviors in other cultures that both cultures share, making the same behavior heroic in one's own culture while making it monstrous in the other culture.
For example: Medusa is turned into a monster because she thinks of herself as beautiful; male Greek heroes are always described as physically beautiful and to be boastful and proud of one's physical prowess, strength and beauty was not only acceptable for men, but expected (see also Beowulf and Gilgamesh, and also male athletes today). Clytemnestra's sexuality is blamed for Agamemnon, her husband's, death, amid a story in which Odysseus enjoys half a dozen sexual partners...and Agamemnon himself returns home with a hot slave chick, Cassandra. The word "Crusade" and "Jihad" have essentially the same meaning, but our reception to them as good/evil depends entirely upon whether or not we are Western-Christian or Eastern-Muslim.
Controlling the representation controls perception: As a rule of thumb, he (or she!) who controls the representation controls the Othering process; whoever tells the story, writes the myth or produces the film, etc., decides who will be Othered/demonized/"the monster" and who will be the hero...and it is very rare for a culture to make themselves the monster.
The battle over ideas -- right/wrong, good/bad, war/not war, my religion/your religion etc. -- is sometimes fought on the battle field, sometimes fought in the courtroom etc., but even then, it is always fought via representation or ideology. Controlling the representation or ideology controls perception and controlling perception controls choice. This is Achebe's point in Things Fall Apart: Europeans are able to dominate African people by changing the African conception of religion and justice; by "Othering" native African religious beliefs, Europeans could gain control over African leaders and, thus, their land and natural resources.
Wo-men, Feminism And The Other: Also see Simone De Beauvoir "The Second Sex" [Woman As Other] (pg 2216)