One version is a person who just predicts the future. In the religious context, I think this too narrow and not a very useful definition.
A second version is an otherwise normal individual who has the gift of prophecy. To me, this is more like someone who's very good at listening to the HS, and might be called "inspired." They do not speak with the authority of God, even though they are tapped into the HS. (This is what you're referring to, yes, Sojourner?)
A third version is people like the Biblical "minor prophets." They get a message from God more directly than us mere individuals who have the gift of prophesy. They speak with authority, but they call people back to a religion that already exists.
A fourth version is people that start entire new religions, like Moses, Jesus, Krishna, Zoroaster, Muhammad, and Baha'u'llah. Like the minor prophets, they appear to be different than just a person who has the gift of prophesy. They do NOT call people back to an existing religion -- they build upon an existing one. They also speak with authority, but unlike minor prophets, they have the authority to overturn social laws* that have outlived their usefulness, and add new social laws that are needed for the times.
*Social law: laws such as marriage and divorce laws, inheritance laws, dietary laws, details on how and when to pray, etc.
*Universal law: Core laws that demand honesty, loving your neighbor, treating others well, that are present in all religions.