From: APA Dictionary of Psychology:
1. in psychoanalytic theory, an object toward which a component instinct is directed. Such an object is usually a part of the body rather than a whole person.
2. in the object relations theory of Melanie Klein, an early object representation that derives from splitting the object into parts containing negative and positive qualities. It is held that such objects constitute the infant’s first experience of the world, being perceived as a good object or a bad object according to whether they are gratifying or frustrating. Internalization of part-objects is further posited to represent the beginning of the inner world of objects whose relationships create the infant’s personality.”