a.
1.
Eager, zealous, ardent, earnest, fervid, vehement.
2.
Sharp, acute, with a fine edge.
3.
Piercing, penetrating, cutting.
4.
Severe, bitter, poignant, acrimonious, caustic.
5.
Shrewd, discerning, quick, sagacious, astute, ~-sighted, ~-eyed, clear-sighted, long-headed.