DavidFilmer said, “Others (including me) define ‘cult’ as a group which is centered around a particular individual (David Koresh, Jim Jones, etc).”
As other posters have noted, this definition would probably include Christianity itself because it is centered around one individual - Jesus Christ.
I agree with Aelred Minor that the definition of “cult” has become subjective at best and in today’s culture is probably more a pejorative label than being representative of anything truly objective.
From my perspective as a Mormon, I think that “Dr.” Walter Martin did as much as anyone to co-opt the term and give it the negative definition that comes to most of our minds today (The Rise of the Cults, 1955; Walter Martin’s Cults Reference Bible, 1976; Walter Martin Speaks out on the Cults, 1981; The New Cults, 1984; and his magnum opus The Kingdom of the Cults, 1985 [with many other editions that followed]). He says “It is typical of cults that they blind their followers to the truth and alienate them from a saving relationship with Jesus Christ.”
There used to be published in Oklahoma (maybe still is) an anti-Mormon paper The Evangel, that charged Mormonism with being a cult because it is excessively devoted to one person, it adds to the word of God, it requires works in addition to grace, it uses unethically manipulative techniques of persuasion and control, it tells its members that it and they are good while the ouside world is evil, and because such usage is generally accepted: “practically everyone who writes on the American cults includes Mormonism” (see Offenders for a Word - How Anti-Mormons Play Word Games to Attack the Latter-day Saints by Daniel C. Peterson and Stephen D. Ricks, p. 199).
So for me, our buddies in the “counter-cult ministries” that are a subset of Evangelical Christianity are the ones to thank for redefining the term in our day. Unfortunately, they tend to crack on you Catholics almost as much as we Mormons, but not to the same extent because of things like your shared acceptance of the concept of Trinity, which we do not embrace.