First, the oldest (and most authentic) meaning --- rarely used anymore --- is simply the worship given to God and the veneration shown toward holy people, places, and things. From the Latin word "cultus." It has no derogatory connotations, not does it imply error or idolatry. In European languages related to Latin it is used in this valid and perfectly neutral sense. For instance, you'll find Protestant churches in Paris which have proudly put these words on their signage out front: Église du Culte Protestant Évangélique.
Second, it is used by many to indicate an emotionally manipulative, secretive, maybe sexually and financially abusive, authoritarian group, whether religious or not: People's Temple, Guru Rajneesh, Synanon, Westboro Baptist, ISKCON, Lyndon Larouche, Kabbala, White Identity, etc.
Third, it is used as a short (but misleading) synonym for self-described Christian groups with (generally) a non-Nicene Christology: Jehovah's Witnesses, Christian Science, Mormon, Seventh Day Adventist, Theosophy.
That's why I don't use the term. You don't know whether the word is used to indicate that the labeled group is (1)devoted to the veneration of the holy, (2) abusive, or (3) just doctrinally at variance with historic Christianity.