The parental alienation syndrome (PAS) is a childhood disorder that arises almost exclusively in the context of child-custody disputes. Its primary manifestation is the child’s campaign of denigration against a parent, a campaign that has no justification. It results from the combination of a programming (brainwashing) parent’s indoctrinations and the child’s own contributions to the vilification of the target parent. When true parental abuse and/or neglect is present, the child’s animosity may be justified and so the parental alienation syndrome explanation for the child’s hostility is not applicable.
Definition sourced from Richard Gardner's Website.