mys·te·ri·ous 
(mĭ-stîrē-əs)
(mĭ-stîrē-əs)adj.
1. Of, relating to, or being a religious mystery: mysterious and infinite truths.
2. Arousing wonder or curiosity, especially by being difficult to explain or understand: the mysterious disappearance of the relevant files.
[French mystérieux, from mystère, secret, from Latin mystērium; see MYSTERY1.]
mys·teri·ous·ly adv.
mys·teri·ous·ness n.
Synonyms: mysterious, esoteric, arcane, occult, cryptic, enigmatic
These adjectives mean beyond human power to explain or understand. Something mysterious arouses wonder and inquisitiveness: "The sea lies all about us.... In its mysterious past it encompasses all the dim origins of life" (Rachel Carson).
What is esoteric is mysterious because only a select group knows and understands it: a compilation of esoteric philosophical essays. Arcane applies to what is hidden from general knowledge: arcane economic theories. Occult suggests knowledge reputedly gained only by secret, magical, or supernatural means: an occult rite. Cryptic suggests a sometimes deliberately puzzling terseness: His roommate left cryptic messages alluding to his whereabouts. Something enigmatic is mysterious and puzzling: The biography struggles to make sense of the artist's enigmatic life.
These adjectives mean beyond human power to explain or understand. Something mysterious arouses wonder and inquisitiveness: "The sea lies all about us.... In its mysterious past it encompasses all the dim origins of life" (Rachel Carson).
What is esoteric is mysterious because only a select group knows and understands it: a compilation of esoteric philosophical essays. Arcane applies to what is hidden from general knowledge: arcane economic theories. Occult suggests knowledge reputedly gained only by secret, magical, or supernatural means: an occult rite. Cryptic suggests a sometimes deliberately puzzling terseness: His roommate left cryptic messages alluding to his whereabouts. Something enigmatic is mysterious and puzzling: The biography struggles to make sense of the artist's enigmatic life.