The noun abomination means a thing or action that is vile, vicious or terrible. For example, if you see a neighbor kick an old blind dog that's done nothing wrong, you might remark, "That kind of cruelty is an abomination!"
The word abomination comes from the Old French word abominacion, meaning "horror, repugnance, disgust." The word abomination can also be used to refer to a person or object you find utterly loathsome and repellent. If you look at someone else as an abomination, that means you are horrified by them, and barely even think they're human. If you hear a friend describing you as an abomination behind your back, you need to find a new buddy right away!