According to Merriam-Webster, a cult is simply a system of religious beliefs and ritual. In general, a cult is a group that claims to belong to a specific religion but misrepresents any core teaching that would prevent a believer from being saved according to that religion. In Christian terms, a cult is "a religious group that denies one or more of the fundamentals of biblical truth." Specifically, it is a group that claims to be Christian, but whose teaching, if believed, would prevent someone from having a saving relationship with Jesus Christ.
What is the definition of a cult?
The core of the Christian salvation message is that Jesus Christ is both God and perfect man, that He died and rose again, and that His sacrifice is solely sufficient to pay for our sins and restore our relationship with God. If any group claims to be Christian but deviates from this message, they are a cult. While many Christian sects differ on minor matters, those who teach a different gospel are not Christian. A Christian sect may believe that Christians are obligated to observe the Sabbath; a cult would teach that honoring the Sabbath is a requirement for salvation.
The two most common Christian cult teachings are that Jesus was not God and that salvation is not by faith alone. Both lead to the belief that Jesus' sacrifice was not sufficient to pay for our sins, and our effort is needed in the process of salvation, which is directly contrary to Scripture (Ephesians 2:8-9). The two most prominent churches who teach this are the Mormons and the Jehovah's Witnesses. Mormons teach that Jesus is not God, and that even God had to earn His position as Supreme Being. Jehovah's Witnesses believe Jesus is Michael the archangel. Both cults teach that salvation is the result of faith and those good works which are listed by their respective churches.
Cults are nearly as old as the church, itself. They're particularly dangerous because they may use the same language and claim to be Christian, but their teachings pull people away from God instead of drawing people toward Him. Their words sound right, their adherents are sincere, but their way leads to death (Galatians 1:6-9).
What is the key to recognizing false teachers?
Is there a good way to evangelize to people in cults or false religions?
What is organized religion and does the Bible support it?
Why are there so many religions?
What is Christian tolerance? Should Christians be tolerant of other religious beliefs?
Truth about Religion