Of facts or matters of knowledge: Unknown; also, not certainly known, uncertain. Obsolete.

Impossible to seize or lay hold of.

That cannot be grasped by the understanding; beyond the reach of intellect or research; unfathomable by the mind. Obsolete or archaic except as in…

That cannot be searched into, so as to be ascertained or exactly estimated; inscrutable.

That cannot be known or understood; beyond comprehension.

Impossible to trace, discover, understand, or examine; unsearchable, unfathomable; inscrutable; = uninvestigable, adj.

= incomprehensible, adj.

Incapable of being framed or grasped by thought; incogitable.

That cannot be searched into or understood through investigation; inscrutable, mysterious.

That cannot be searched into or found out by searching; impenetrable or unfathomable to investigation; quite unintelligible, entirely mysterious.

Not opinable; unthinkable, inconceivable; not to be thought of.

= incomprehensible, adj.

Incapable of being regarded.

Unthinkable, inconceivable.

(un-, prefix1 affix 1b.)

transferred and figurative. Whose nature, meaning, etc. cannot be penetrated or discerned; inscrutable; unfathomable. Of things.

Unimaginable.

That cannot be unfolded, untwisted, or disentangled; inextricable; very intricate or complex. Obsolete.

= insensible, adj. 2.

(un-, prefix1 affix 1b.)

Incapable of being fashioned or shaped; not admitting of a material form. Obsolete.

Incapable of being penetrated; impenetrable.

(un-, prefix1 affix 1b.)

That must not be uttered; †not to be disclosed or made known (obsolete).

Incapable of being excogitated; inconceivable, incogitable.

Not divinable; incapable of being divined.

That cannot be investigated or traced out.

That cannot be received or apprehended. Const. to. Obsolete. rare.

Unable to be clearly understood; resisting investigation; inscrutable, unsearchable.

That cannot be comprehended. Obsolete.

Inconceivable. (Common in 17–18th centuries.)

(un-, prefix1 affix 1b.)

Incapable of being imagined; inconceivable, incomprehensible.

= inexplicable, adj. 1.

Not intelligible; incapable of being understood. Also absol.

That cannot be apprehended.

figurative. Of feelings, qualities, conditions, etc.: Incapable of being fully ascertained, explored, exhausted, etc.

Not to be grasped or seized; not to be apprehended.

(un-, prefix1 affix 1b.)

Incapable of being mentally apprehended or detected; undiscoverable.

Incapable of being discerned by the senses or intellect; imperceptible; undiscoverable.

= inscrutable, adj.

Not apprehensible; that cannot be apprehended or grasped by the senses or intellect.

Not discoverable; not to be found out; undiscoverable.

(un-, prefix1 affix 1b.)

That cannot be sought into, examined, or understood; uninvestigable. Cf. investigable, adj.1

figurative. That cannot be penetrated or fully understood; incomprehensible. Cf. fathom, v. 4b.

That cannot be conceived or realized in the imagination; unthinkable, unimaginable, incredible. Often with exaggerative force for ‘hardly credible’…

Incapable of being definitely fixed or ascertained.

That cannot be explored; inscrutable.

That cannot be searched out; unsearchable.

Not comprehended; beyond comprehension.

Incomprehensible.

Not to be comprehended or understood; incomprehensible. Obsolete.

(un-, prefix1 affix 1b.)

(un-, prefix1 affix 1b.)

Unintelligible. Obsolete.

Unknowable, beyond cognizance.

With participles, as thought-abhorring, thought-engendering, thought-inspiring, thought-reviving, thought-saving, thought-transcending, etc.

(un-, prefix1 affix 1b.)

Incomprehensible, unknowable.

(un-, prefix1 affix 1.)

That eludes the grasp or pursuit; chiefly figurative.

figurative. Incapable of being (readily) grasped or apprehended by the mind; producing no definite mental impression; ‘intangible’.

Of an emotion, a concept, etc.: that is impossible to apprehend or get in touch with. Also with to.

(un-, prefix1 affix 1b.)

(un-, prefix1 affix 1.)

(un-, prefix1 affix 1b.)

(un-, prefix1 affix 1b.)

(un-, prefix1 affix 1b.)

Not realizable (in various senses of realize, v.2).

(un-, prefix1 affix 1b.)

figurative. Difficult to solve or penetrate; intractable. Now rare.

(un-, prefix1 affix 1.)

Unsuspected, unimagined.

Not admitting of a grasp, i.e. of being grasped.

(un-, prefix1 affix 2.)

Not cognizable; incapable of being known, perceived, or apprehended by the senses or intellect; incapable of recognition.

(un-, prefix1 affix 1b.)

Of a face, remark, character, etc.: that cannot be interpreted; inscrutable.

That is above or beyond the range of the human intellect. Now rare.

Of an object of thought: That eludes the mental grasp; that one cannot ‘get hold of’.

That is beyond or outside of consciousness or cognition.

figurative. That cannot be grasped mentally.

(un-, prefix1 affix 1b.)

(un-, prefix1 affix 2b.)

Unfathomable; immeasurably deep.

literary. That cannot be known or understood; incomprehensible. Obsolete. rare.

= indiscussible, adj.