a. 难以了解的, 不能预测的

[法] 不可理解的, 不可思议的, 不可测知的

[ adj ]
of an obscure nature
<adj.all>
the new insurance policy is written without cryptic or mysterious termsa deep dark secret
the inscrutable workings of Providence
in its mysterious past it encompasses all the dim origins of life
rituals totally mystifying to visitors from other lands

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