Often with a prepositional phrase, or with to and an infinitive: showing a quick and ardent responsiveness or willingness; eager, enthusiastic, interested.
I’m keen on computers.
Fierce, intense, vehement.
This boy has a keen appetite.
Having a fine edge or point; sharp.
Acute of mind, having or expressing mental acuteness; penetrating, sharp.
Acrimonious, bitter, piercing.
keen satire or sarcasm
Of cold, wind, etc.: cutting, penetrating, piercing, sharp.
a keen wind
Of prices, extremely low as to be competitive.
Marvelous.
I just got this peachy keen new dress.
Brave, courageous; audacious, bold.