keen 1 
(kēn)
(kēn)adj. keen·er, keen·est
1. Having a fine, sharp cutting edge or point.
2. Having or marked by intellectual quickness and acuity. See Synonyms at sharp.
3. Acutely sensitive: a keen ear.
4. Sharp; vivid; strong: "His entire body hungered for keen sensation, something exciting" (Richard Wright).
5. Intense or bracing: a keen wind.
6. Pungent; acrid: A keen smell of skunk was left behind.
7.
a. Ardent; enthusiastic: a keen chess player.
b. Eagerly desirous: keen on going to Europe in the spring.
8. Slang Great; splendid; fine: What a keen day!
[Middle English kene, from Old English cēne, brave.]
keenly adv.
keenness n.