mordant

This word carries a dual energy of chemical erosion and intellectual sharpness. When used to describe a person's tone, it suggests a level of sarcasm that is not merely playful but is intended to cut through pretense or expose a harsh truth. It is far more aggressive than "witty" and more calculated than "mean." In a technical sense, the term describes a substance that creates a permanent bond. This creates a linguistic link between the way a chemical "bites" into fabric to hold color and the way a caustic comment "bites" into a subject to leave a lasting, often painful, impression.