Keen, a. [Compar. Keener; superl. Keenest.]
Etymology: [OE. kene sharp, bold, AS.c bold; akin to D. koen, OHG. kuoni, G. kühn, OSw. kyn, kön, Icel. kænn, for koenn wise; perh. akin to E. ken, can to be able.
1. Sharp; having a fine edge or point; as, a keen razor, or a razor with a keen edge. A bow he bare and arwes [arrows] bright and kene. Chaucer. That my keen knife see not the wound it makes. Shak.
2. Acute of mind; sharp; penetrating; having or expressing mental acuteness; as, a man of keen understanding; a keen look; keen features. To make our wits more keen. Shak. Before the keen inquiry of her thought. Cowper.
3. Bitter; piercing; acrimonious; cutting; stinging; severe; as, keen satire or sarcasm. Good father cardinal, cry thou amen To my keen curses. Shak.
4. Piercing; penetrating; cutting; sharp; -- applied to cold, wind, etc, ; as, a keen wind; the cold is very keen. Breasts the keen air, and carols as he goes. Goldsmith.
3 more senses
5. Eager; vehement; fierce; as, a keen appetite. "Of full kene will." Piers Plowman. So keen and greedy to confound a man. Shak.
Note: Keen is often used in the composition of words, most of which are of obvious signification; as, keen-edged, keen-eyed, keen- sighted, keen-witted, etc.
Syn. -- Prompt; eager; ardent; sharp; acute; cutting; penetrating; biting; severe; sarcastic; satirical; piercing; shrewd.
3 other Webster entries under this spelling
Keen, v. t.
To sharpen; to make cold. [R.] Cold winter keens the brightening flood. Thomson.
Keen, n.
A prolonged wail for a deceased person. Cf. Coranach. [Ireland] Froude.
Keen, v. i.
To wail as a keener does. [Ireland]
Shades of meaning
Fernald has no entry of its own for keen; he lists it under astute, clever, eager, fine, sagacious.
Where he writes about it:
Acute, from the Latin, suggests the sharpness of the needle's point; keen, from the Saxon, the sharpness of the cutting edge. — from astute
Astute, from the Latin, with the original sense of cunning has come to have a meaning that combines the sense of acute or keen with that of sagacious. — from astute
The acute, keen intellect may take no special advantage of these qualities; the astute mind has always a point to make for itself, and seldom fails to make it. — from astute
As that which is delicate is apt to be small, by an easy extension of meaning fine becomes a synonym for slender, slight, minute, comminuted; as, a fine thread, fine sand; or for filmy, tenuous, thin; as, a fine lace, fine wire; and as a thin edge is keen, sharp, fine becomes also a synonym for these words; as, a fine point, a fine edge. — from fine