mystery

1. (obsolete) A secret or mystical meaning.Examples: "[…] and, not knowing the meaning or misterie of her pollicie, forgat no termes of reproche or rigorous rebuke against his chast doughter."countableobsoleteuncountable

2. (archaic outside Eastern Orthodoxy) A sacrament.Examples: "There are seven mysteries, or sacraments, in the Greek church, viz. baptism, the chrism (a rite peculiar to this church), the eucharist, confession, ordination, marriage, and the holy oil."countableuncountable

3. (chiefly in the plural) A secret religious celebration, admission to which was usually through initiation.Examples: "the Eleusinian mysteries"; "the Mysteries of Mithras"; "There’s no initiation either into such mysteries."countablein-pluraluncountable

4. (Catholicism) A particular event or series of events in the life of Christ.Examples: "The second decade of the Rosary concerns the Sorrowful mysteries, such as the crucifixion and the crowning with thorns."countableuncountable

5. (archaic) A craft, art or trade; specifically a guild of craftsmen.Examples: "The trades, the crafts, the mysteries, would all be losers."archaiccountableuncountable