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.
5. Eager; vehement; fierce; as, a keen appetite. "Of full kene will." Piers Plowman.
"So keen and greedy to confound a man." -- Shak.
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.