Inscrutable
Pronunciation : In*scru"ta*ble
Part of Speech : a.
Etymology : [L. inscrutabilis : cf. F. inscrutable. See In- not, and Scrutiny.]
Definition : Defn: 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