mys·ter·y

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun One that is not fully understood or that baffles or eludes the understanding; an enigma.
• noun One whose identity is unknown and who arouses curiosity.
• noun A mysterious character or quality.
• noun A work of fiction, a drama, or a film dealing with a puzzling crime.
• noun A religious cult practicing secret rites to which only initiates are admitted.
• noun A secret rite of such a cult.
• noun A religious truth that is incomprehensible to reason and knowable only through divine revelation.
• noun An incident from the life of Jesus, especially the Incarnation, Passion, Crucifixion, or Resurrection, of particular importance for redemption.
• noun One of the 15 incidents from the lives of Jesus or the Blessed Virgin Mary, such as the Annunciation or the Ascension, serving in Roman Catholicism as the subject of meditation during recitation of the rosary.
• noun One of the sacraments, especially the Eucharist.
• noun The consecrated elements of the Eucharist.
• noun The skills, lore, or practices that are peculiar to a particular activity or group and are regarded as the special province of initiates.
• noun A mystery play.
• noun A trade or occupation.
• noun A guild, as of merchants or artisans.