Keen

agudo

(acute of mind)

aguzado

(acute of mind)

ardoroso

(showing a quick and ardent responsiveness or willingness)

cortante

(of cold, wind, etc.: cutting, penetrating)

entusiasmado

(showing a quick and ardent responsiveness or willingness)

entusiasta

(showing a quick and ardent responsiveness or willingness)

fijo

(showing a quick and ardent responsiveness or willingness)

interesado

(showing a quick and ardent responsiveness or willingness)

motivado

(showing a quick and ardent responsiveness or willingness)

vehemente

(fierce, intense, vehement)

voraz

(fierce, intense, vehement)