Synonyms For "Keen" :
1 syllable:
great, neat, old, sharp, swell
2 syllables:
acute, bully, corking, cracking, cutting, dandy, groovy, knifelike, lament, nifty, not bad, peachy, piercing, smashing, stabbing
3 syllables:
exquisite, incisive, lancinate, perceptive
4 syllables:
lancinating, penetrating, penetrative