Definitions for "Mystery Religion"
Any religion with an arcanum, or body of secret wisdom. In a mystery religion, an inner core of beliefs, practices, and the religion's true nature, are revealed only to those who have been initiated into its secrets. These secrets are not to be profaned (pro + fanum "beyond the fane, or religious precinct"). By their very nature mysteries are ineffable, beyond what can be expressed in words, or esoteric.
a belief system based around a mystery In medieval Britain , mystery meant a craft , trade or profession
a religion the true nature of whose beliefs and practices is known only to those who have been initiated into its secrets
a metaphoric representation of decay and revival, of descent to hell and ascension to heavens of some mystery deity, as the warrantee for the salvific expectations, the eternal life, of the believers