Whether any group is a "cult" depends on how you define the word "cult." Many religious people define as "cult" any group that has beliefs or teachings that they consider heretical (that is, not like their own). Often that definition is phrased as: "A cult teaches false doctrine." That is not a useful definition.
For cult experts (people who deal professionally with cults as harmful and oppressive organizations) it is not really the content of the organization's doctrine that puts them in the "cult" category so much as the techniques they use to attract and to keep members. Those professionals have usually drawn up checklists of cult characteristics, against which anyone can measure how cult-like an organization is.
The following is a synthesis of the major characteristics of cults, based on many checklists from cult experts.
Cult Characteristics
The group displays unquestioning commitment to its leader and (whether he is alive or dead) regards his belief system, ideology, and practices as the binding truth and law.
Questioning, doubt, critical thinking, and dissent are discouraged or even punished.
Mind-altering practices (such as meditation, chanting, speaking in tongues, denunciation sessions, and debilitating work routines) are used in excess to solidify loyalty to the group.
The leadership dictates, sometimes in great detail, aspects of daily life: how members should think, act, and feel, how they should dress, what they should eat.
The group is elitist, claiming a special, exalted status for itself, its leader(s) and members, as the sole depository of the complete truth. No other belief system is seen as legitimate or useful.
The group has a polarized us-versus-them mentality.
The group sees itself as persecuted because of its having the truth, and views any criticism from outside as evidence of persecution and thus confirmation of the group's truth.
The group fosters either-or, black-and-white views, right-or-wrong thinking, with no allowance for gray areas.
The leader is not accountable to any authorities or to the members.
The group teaches or implies that its supposedly exalted ends justify whatever means it deems necessary, which may result in members' participating in behaviors or activities they would have considered reprehensible or unethical before joining the group.
The leadership induces feelings of shame, guilt, and/or fear in order to influence and/or control members.
Members who have difficulties conforming to the group are made to feel that the problems are because of their own failings, and not because of any problems with the group.
Subservience to the leader or group leads members to cut ties with family and former friends, and to alter radically the personal goals and activities they had before joining the group.
The group expends great effort to bring in new members.
The group requires major financial commitment from its members as a test of loyalty to the group.
Members are expected to devote inordinate amounts of time to the group and group-related activities.
Members are encouraged or required to live and/or socialize only with other group members.
Members are encouraged to report to the leadership group members who are not conforming.
The group has an extensive system of rewards and punishments for controlling members' lives.
Leadership uses deception, both to the public and to its own members.
The group has special vocabulary, a kind of shorthand, or "buzz words" which substitute for actual rational analysis.
Leadership exerts control over information, discouraging members from getting information from non-group sources. Some important information is not available to new members, but only those who have proven their loyalty.
Members come to feel there can be no life outside the context of the group. They believe there is no other way to live, and often fear severe consequences if they leave (or even consider leaving) the group.
This list is based primarily on Characteristics Associated with Cultic Groups - Revised" by Janja Lalich, Ph.D. & Michael D. Langone, Ph.D., also in Take Back Your Life: Recovering from Cults and Abusive Relationships (Paperback) by Janja Lalich, Madeleine Landau Tobias ISBN: 0972002154
Other resources on identifying cults, with similar checklists:
http://www.freedomofmind.com/ The home page of Steve Hassan, an authority on cults and brainwashing.
"[Hassan's] BITE Model Applied Toward Mormonism"
http://www.caic.org.au Jan Groenveld's Cult Awareness Centre
http://www.factnet.org FACTnet, resources on psychological coercion and mind control
http://www.neopagan.net/ABCDEF.html Isaac Bonewits' cult checklist, with 18 items and worksheet.
A 12-minute video on cults in general:
http://www.youtube.com/watch?v=mnNSe5XYp6ELuna Lindsey, Recovering Agency: Lifting the Veil of Mormon Mind Control, 2014
See also the article "Spiritual Abuse"
Mormonism has many cult characteristics, to varying degrees. My evaluation is at packham.n4m.org/cult.htm