Not tractable; not able to be managed, controlled, governed or directed.
Difficult to treat (of a medical condition).
Difficult to deal with, solve, or manage.
(of a mathematical problem) Not able to be solved.
Stubborn; obstinate.
That cannot be investigated or searched into; unknowable, inscrutable.
Not capable of being searched; on which one cannot perform a search.
That cannot be sought out or looked for.