1. intellectually alert having or characteristic of a quick penetrating mind
a keen student a keen awareness of the problem also shrewdly astute
a keen assessment
2. extremely sensitive in perception
keen eyes a keen sense of smell
3. sharply contested
keen competition keen debate
4. showing a quick and ardent responsiveness enthusiastic
a keen swimmer
5. eager
was keen to begin
6. intense
the keen delight in the chase
— F. W. Maitland
7. wonderful, excellent
a keen idea
8. having a fine edge or point sharp
a knife with a keen blade
9. affecting one as if by cutting
keen sarcasm
10. pungent to the sense
a keen scent
11. very enthusiastic or excited about
wasn't keen on going
12. to make a loud and long cry of sorrow to lament with a keen
13. to make a sound suggestive of a loud cry of sorrow
a keening siren
14. to lament, mourn, or complain loudly
15. to utter with a loud wailing voice or wordless cry
keened our sorrow
— Punch
16. a lamentation for the dead uttered in a loud wailing voice or sometimes in a wordless cry
17. having or showing an ability to think clearly and to understand what is not obvious or simple about something
18. very strong and sensitive highly developed
19. very excited about and interested in something
20. to make a loud and long cry of sorrow
21. having a fine edge or point sharp
a keen knife
22. having or showing mental sharpness
a keen observation
23. very sensitive (as in seeing, smelling, or hearing)
keen eyesight
24. full of enthusiasm eager
… everybody was very keen to hear details of what had happened …
— J. K. Rowling, Goblet of Fire
25. seeming to cut or sting
a keen wind