That is mystic or mystical which has associated with it some hidden or recondite meaning, especially of a religious kind; as, the mystic Babylon of the Apocalypse.

J. C. Fernald, English Synonyms and Antonyms (1914)

Example sentences

mysterious A mysterious spaceship was flying away from Earth.
esoteric Kabbalah is an esoteric tradition within Judaism.
enigmatic She's a strange, enigmatic and inspiring poet.
magical Ivan told Rima that Walid was a magical therapist.
mystical Swamps are no fun to tread in, but they can be mystical.

Popularity over time

Word	1850 → 2019	Trend
mystic		steady
mysterious		rising
esoteric		rising
enigmatic		rising
arcane		rising
magical		rising

Use in printed books, per decade from 1850 to 2019.

By length

4 letters: dark¹, mage
6 letters: secret², hidden², wizard², occult², latent², arcane²
7 letters: magical³, obscure², cryptic²
8 letters: mystical³, magician³, esoteric⁴, abstruse², numinous
9 letters: enigmatic⁴, insoluble⁴, recondite³, sorcerous, mysterial
10 letters: mysterious⁴, unknowable⁴, symbolical
11 letters: allegorical⁵, inscrutable⁴, clairvoyant³, kabbalistic
12 letters: inexplicable⁵, sortilegious, thaumaturgic

The small number after each word is its number of syllables (secret² = 2 syllables).

In other languages

Français: mystique
Italiano: mistico
Deutsch: mystisch