The problem with defining a cult is that the modern English usage of the word has been both narrowed and widened in meaning at the same time. By narrowed, I mean it is saved to be applied to groups seen as dangerously and weirdly deviant from the supposed norm. But it is widened, because with the prospering of it’s negative connotations, it is being cast about to include any group that 1) does not pass certain political standards or 2) shows signs and symptoms of basic human flaws.
Cult is etymologically related to the words culture and cultivate. It’s strong religious connotations come from the fact that it originally simply referred to a system of ritual practices of worship directed toward any so-called god, true or false. (See etymonline.com and Webster’s New World College Dictionary, 4th edition.) The relationship with the deity was “cultivated,” cared for, labored for by certain conduct to obtain a certain result. This devotion was recognizable as the worship rituals associated with a particular group. Up until the 17th century, it was just a matter of “cultural” differences, and not thought of as particularly meaning the group was deluded. If they were thought to be deluded, that was another matter. The explanation of the Latin root, cultus, includes “reverent and respectful treatment of the gods.” (Cassell’s Latin Dictionary)
The more current meaning of the word cult usually implies an unusual degree of attachment to a charismatic person or a set of beliefs that others view as extreme. And there you find the crux of the problem. The label of “cult” is a completely subjective one. If someone thinks people are too devoted or “outside the mainstream” of whatever, they are marginalized by calling them a cult. It all comes down to what you think the truth is and how you think people should, or shouldn’t, interact. This is the meaning that has been growing since the early 19th century. If you are noticing a gap in the time sequence, you are correct. Apparently, the word cult was ignored during the 18th century.
There are a few places in the Bible where the word cult is used. Well, in the English Standard Version, the New American Standard Bible, and the Revised Standard Version translations of the Bible. In all of these translations, the word cult is in the Old Testament and linked to the word prostitute. This word study on original Hebrew of those passages makes a good case for the use of the word cult here being a misleading, and almost pointless assumption. It doesn’t make a difference in the message of the Bible, but it could affect your understanding of the word cult because it drastically weakens the link between the ideas of cults and prostitution; and leaves us with figuring out the only two places in the New Testament where the word cult is used.
It is only in the paraphrase/translation called the New Living Testament (out of the 7 most common versions that I looked at) that the word cult is used in the New Testament. Here, it is used for the same Greek word that is translated sect or heresy in other Bible translations. Sect is used in other parts of the Biblical account, too, where cult is not used in any version. The Sadducees and the Pharisees are referred to as sects more in the sense of “divisions of thought.” Paul himself refers to the Pharisees this way in Acts 26:5. In Acts 24:5, he is accused of being part of the sect of the Nazarenes. In 1 Corinthians 11:19, Paul states that “factions,” which could also be translated “sects,” will rise up among them to help them distinguish those who should be respected.
Sect and heresy are both translated from the same Greek word, hairesis, which literally means “a choosing.” The connotation, according to Vine’s Expository Dictionary, is that there has been a “choosing” that creates division, based on a desire for personal gain or a willingness to depart from the truth because of personal preference. The truth would unite people, if applied.
Unbalanced application of otherwise truthful ideas or following after a person regardless of truth tend to lead to self-righteous and/or exclusionary lifestyles. However, it could be argued that self-righteous attitudes and exclusionary participation in selective groups are so common that it is almost laughable to call any particular group a cult in the modern sense. Everyone is a cult if you disagree with them. Normal or average do not stand up well to examination, proving to be an illusion or purely statistical measurement not to be found in real life.
It seems it would be more useful to just describe what is going on, or what is observed in how people are treated, than to use the word cult. Much like the word abuse. If someone took you by the arms and told you not say something or you are going to be locked in a room or expelled from position, that is very clear. If someone punches you in the stomach, that is also a clear picture. No need to use fuzzy words like cult.
The Biblical meaning of sect also makes it seem more like many religious organizations are all about division rather than unity. It is not a huge leap to see them all calling each other “cults.” It bears repeating: The truth unites. It is human failure that causes division. Human failure is a constant and does not have to be labeled as a cult to be destructive.