Incomprehensible, a.
Etymology: [L. incomprehensibilis: cf. F. incompréhensible. See In- not, and Comprehensible.]
1. Not capable of being contained within limits. An infinite and incomprehensible substance. Hooker.
2. Not capable of being comprehended or understood; beyond the reach of the human intellect; inconceivable. And all her numbered stars that seem to roll Spaces incomprehensible. Milton. -- In*com`pre*hen"si*ble*ness, n. -- In*com`pre*hen"si*bly, adv.
Shades of meaning
Fernald has no entry of its own for incomprehensible; he lists it under mysterious, obscure.
He lists it without comment; the entries above explain its neighbors.