1. | a particular system of religious worship, esp. with reference to its rites and ceremonies |
The above is the first definition of cult on dictionary.com. That sounds like the catholic church would be a cult.
4. | a group or sect bound together by veneration of the same thing, person, ideal, etc. This could be catholics, baptist, pentacostals |
6. | 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. |