As sharp as a razor; extremely sharp. / (idiomatic) Very clever or quick-witted.

Having acute vision; having good eyesight. / Attentive, given to noticing things, aware.

Having an acrid or bitter wit. Often said of someone skilled at or given to insulting or belittling others.

Clever, keen of intellect, swift of thought.

Very sharp; as sharp as a needle / (of a sound) very high-pitched.

Commercial activity that is possibly dishonest while not actually being illegal. / (law) A lawyer's unfairly taking advantage of an opposing party's missteps or inexperience to gain an advantage.

Having a sharp point

(idiomatic) The practice or characteristic of speaking to others in a harsh, critical, or insulting manner.

(simile, colloquial) very intelligent

(music) In microtonal music, a note played three quarter tones higher than a natural.