1. Eager; vehement; as hungry curs too keen at the sport.
The sheep were so keen on the acorns--
2. Eager; sharp; as a keen appetite.
3. Sharp; having a very fine edge; as a keen razor, or a razor with a keen edge. We say a keen edge, but a sharp point.
4. Piercing; penetrating; severe; applied to cold or to wind; as a keen wind; the cold is very keen
5. Bitter; piercing; acrimonious; as keen satire or sarcasm.
Good father cardinal, cry thou amen,
To my keen curses.
KEEN, verb transitive To sharpen. [Unusual.]