Many people confuse a cult with the occult. It gets a little more confusing when the term is applied in different ways. Further more, those in a Cult will sometimes apply the term Christian to themselves. It is still unclear after looking to the Dictionary. For example, Random House Webster's College Dictionary states the following under cult:
2.  a group that devotes itself to or venerates a person, ideal, fad, etc.
3. a.  a religion or sect considered to be false, unorthodox, or extremist. 
By the 2nd definition all of us who follow the Jesus of the Bible would be called a cult. Yet we would call others a cult because of the 3rd definition.
           Generally the occult is applied to those involved in witchcraft or Satan worshipers, although it also would apply to fortune telling, Astrology, tarot cards etc. The confusing part comes when there are those that are not considered part of the occult, yet follow practices, which can be defined as occult such as Masonry or Mormonism. 
Random House Webster's College Dictionary 1996 describes occult:
1. of or pertaining to any system claiming use or knowledge of secret or supernatural powers or agencies.    2. beyond ordinary knowledge or understanding.  3. secret; disclosed or communicated only to the initiated.  4. hidden from view
It is the 3rd & 4th definition here that can be applied to Mormonism or Masonry due to the secret ceremonies that some are involved in.
           Generally speaking those religions that are considered a cult are those religions that do not believe or follow Historic Christianity. The Protestant movement is a part of historic Christianity.  Merriam Webster's Collegiate Dictionary Tenth Edition, 1993 defines Protestant b: a member of any of several church denominations denying the universal authority of the Pope and affirming the Reformation principles of justification by faith alone, the priesthood of all believers, and the primacy of the Bible as the only source of revealed truth;
           Let me explain a little bit of what we mean by Historic Christianity the Doctrines that we find taught in the Bible can be traced throughout history. For Example we have the writings of the Early Church Fathers. These are the men that studied directly under the Apostles and the men that studied under them. These men did a lot of writing. One such man is, Polycarp who studied directly under the Disciple John whose writings is part of the New Testament. The writings of the Early Church Fathers are not considered scripture, but they are valuable just the same. They confirm what the original Disciples taught and believed. It is a good reference to verify if the church today is teaching the same doctrines as the original church that we see developed in the book of Acts. When you study church history you can see that this is what the Reformation period was all about. The church that we see developed in the Bible in the book of Acts evolved into the Catholic Church. The Catholic Church developed their own doctrines or beliefs that were not taught by the original Disciples or found in the Bible. Later men, such as, Martin Luther strongly protested those false doctrines and a movement breaking away from the Catholic church developed. As time went on many denominations ended up developing due to doctrinal issues.