INSCRUTABLE

cryptic, cryptical, deep, inscrutable, mysterious, mystifying

(adjective) of an obscure nature; “the new insurance policy is written without cryptic or mysterious terms”; “a deep dark secret”; “the inscrutable workings of Providence”; “in its mysterious past it encompasses all the dim origins of life”- Rachel Carson; “rituals totally mystifying to visitors from other lands”

Source: WordNet® 3.1

Etymology

Adjective

inscrutable (comparative more inscrutable, superlative most inscrutable)

Difficult or impossible to comprehend, fathom, or interpret.

Synonyms: ineffable, Thesaurus:incomprehensible

Noun

inscrutable (plural inscrutables)

One who or that which is inscrutable; a person, etc. that cannot be comprehended.

Source: Wiktionary

In*scru"ta*ble, a. Etym: [L. inscrutabilis : cf. F. inscrutable. See In- not, and Scrutiny.]

Definition: Unsearchable; incapable of being searched into and understood by inquiry or study; impossible or difficult to be explained or accounted for satisfactorily; obscure; incomprehensible; as, an inscrutable design or event. 'T is not in man To yield a reason for the will of Heaven Which is inscrutable. Beau. & Fl. Waiving a question so inscrutable as this. De Quincey.

Source: Webster’s Unabridged Dictionary 1913 Edition