An excellent academic resource on defining a Cult.

Benjamin Zablocki, 1997: a cult is "an ideological organization held together by charismatic relationships and demanding total commitment."

Cult (totalist type): A group or movement exhibiting a great or excessive devotion or dedication to some person, idea, or thing and employing unethically manipulative techniques of persuasion and control (e.g. isolation from former friends and family, debilitation, use of special methods to heighten suggestibility and subservience, powerful group pressures, information management, suspension of individuality or critical judgment, promotion of total dependency on the group and fear of leaving it, etc.), designed to advance the goals of the group's leaders, to the actual or possible detriment of members,  their families, or the community. (West & Langone, 1986, pp. 119-120)

"Cults are not all alike.   Nor are all cult members affected in the same way, even within the same group.  Nevertheless, a huge body of clinical evidence leads ICSA associates to contend that some groups harm some members sometimes, and that some groups may be more likely to harm members than other groups. "

http://www.csj.org/infoserv_cult101/essay_cult.htm  

THE INTERNATIONAL CULTIC STUDIES ASSOCIATION:

A list of academic resources:

http://www.icsahome.com/elibrary/studyguides/formergroupmembers