Dictionary.com is my favorite online dictionary, especially when used with Firefox.
- a particular system of religious worship, esp. with reference to its rites and ceremonies. Islam satisfies this. Since religion is used in the definition, so does Christianity, Judaism, Baha'i, etc.
- an instance of great veneration of a person, ideal, or thing, esp. as manifested by a body of admirers: the physical fitness cult. Muslims submit to God. Christians place their faith in the Son.
- the object of such devotion. I guess this is used for cult of personality.
- a group or sect bound together by veneration of the same thing, person, ideal, etc. Sure, see my comments on definition two.
- Sociology. a group having a sacred ideology and a set of rites centering around their sacred symbols. See comment two.
- a religion or sect considered to be false, unorthodox, or extremist, with members often living outside of conventional society under the direction of a charismatic leader. Some people here view Islam as such. Except, Muhammad has been dead for over a millenium now and there is no one leader.
- the members of such a religion or sect. If you want to call it one...
- any system for treating human sickness that originated by a person usually claiming to have sole insight into the nature of disease, and that employs methods regarded as unorthodox or unscientific. No.
Under some definitions, Islam could be considered a cult. By the same token, so would Christianity.