Lacking or deficient in wit, intelligence, or knowledge; ignorant, unwise, witless. Now rare.

Lacking understanding; foolish. Cf. heart, n. 12. Now archaic and rare.

Of a person or body of people, a person's condition, etc. (In early use frequently in the comparative.) Inferior in ability, learning…

Lacking awareness or understanding; thoughtless. Also: lacking wit or ingenuity; unlearned. historical in later use.

= insensate, adj.

Lacking sense or understanding; unintelligent, stupid, senseless, foolish.

Destitute of sense or intelligence; irrational.

Uncomprehending, misunderstanding, ignorant; neglectful.

= insensible, adj. 5.

Deficient in understanding; having undeveloped or imperfect intellectual power; unintelligent, undiscerning; stupid, dull-witted.

(un-, prefix1 affix 2b.)

Not apprehending or understanding; dull-witted.

As the characteristic of inanimate things: without sensation, consciousness, thought, or feeling. Now chiefly Philosophy.

That knows or understands little. (In later use only with allusion to quot. 1598.) Cf. all-knowing, adj.

figurative. Not endowed with sense or perception; insensate, unintelligent. Obsolete.

(un-, prefix1 affix 4.)

Incapable of apprehending.

Not perceiving or capable of perceiving; (esp. in early use) lacking in perception or insight; unperceptive.

Not apprehensive or quick to understand; stupid, unintelligent.

That does not apprehend; inapprehensive.

Not understanding; deficient in mental grasp.

Not apprehensive; without apprehension: (a) that does not grasp mentally, or perceive by sense; (b) that does not apprehend danger.

Not having a penetrating quality.

Not possessing intelligence or consciousness; acting without discernment.

Lacking in comprehension.

Not penetrating (in various senses); esp. lacking insight or acuity.

Of the features, a gaze, etc.: expressionless, vacant; (apparently) unintelligent. Now rare (chiefly in historical contexts).

Characterized by, exhibiting, or proceeding from, absence of intelligence or thought; expressionless, meaningless; inane.

Foolish, stupid, awkward.

(un-, prefix1 affix 1.)

Lacking in apprehension.

Not penetrative. Later chiefly (Sport): not capable of breaching an opponent's defence; cf. penetrating, adj. 1d.

Witless.

(un-, prefix1 affix 4.)

Not recognizant; not having recognition.

Empty of ideas; unintelligent; expressionless. Cf. vacant, adj. 5.

Not comprehending; wanting in comprehension or understanding.

Of a person: easily taken in or influenced; stupid.

Foolish, witless. Now rare.

Characteristic of a stupid or foolish person; dumb, dopey. Cf. goofus, adj.

Lacking a brain, that has had the brain removed; (hence) unintelligent, unthinking. Cf. brainless, adj.

(a) having suffered brain death; (b) slang (originally U.S.) lacking in (esp. intellectual) vigour; feeble-minded, stupid, vapid; (also)…

Stupid, foolish. Cf. doofus, adj.