Of the mind and its qualities or operations, esp. wit: alert, active, keenly perceptive; ready, lively, agile.

Of the mind or mental faculties: quick to understand, plan, etc.; alert, perceptive, incisive. Now chiefly in ready wit.

Of the sight, mind, intellect, etc.: sharp, keen; penetrating, incisive; seeing or appearing to see clearly through or into something.

Piercing, penetrative.

That perforates something; that bores or passes through something; penetrating; (Anatomy, of an artery, vein, nerve, or muscle) that passes through…

Acute or penetrating in intellect or perception. Of reasoning or discourse: acute, sagacious. Also, of remarks: pointed, apt, witty.

Of the mind, intellect, etc.: quick to devise or plan; clever, versatile, alert.

Of mental faculties: Quick, sharp. Obsolete.

Of mental faculties: Quick, ready, smart.

Of mental faculties and their operations: Showing apprehension or grasp of a subject; intelligent, discerning, quick.

Of the judgement: Keen, acute.

That resembles or suggests an arrow in flight; arrow-like; (of the mind, a look, etc.) penetrating, piercing.

Of persons: Intellectually acute, sharpwitted, shrewd: often with mixture of sense A. 6. Also of the mind or mental operations: Endowed or conducted…

Having an extremely sharp edge; keen-edged (in quot. figurative).

Of a person or the mind: quick to understand, learn, and think; intelligent, clever. Cf. slow, adj. 2.

Characterized by insight.