Wiktionary
n. (label en Scientology) A person who causes one severe emotional distress and impedes his or her spiritual progress.
Wikipedia
Suppressive Person, often abbreviated SP, is a term used in Scientology to describe the "antisocial personalities" who, according to Scientology's founder L. Ron Hubbard, make up about 2.5% of the population. A statement on a Church of Scientology website describes this group as including notorious historic figures such as Adolf Hitler.
The term is often applied to those whom the Church of Scientology perceives as its enemies, i.e., those whose "disastrous" and "suppressive" acts are said to impede the progress of individual Scientologists or the Scientology movement.
One of the reasons Scientology doctrines portray Suppressive Persons as such a danger is that they are supposed to make people around them become Potential Trouble Sources (abbreviated PTS). Scientology defines a PTS as "a person who is in some way connected to and being adversely affected by a suppressive person. Such a person is called a potential trouble source because he can be a lot of trouble to himself and to others." PTSs are said to make up 17.5% of the population.