caus·tic (kô′stĭk) adj. 1. Capable of burning, corroding, dissolving, or eating away by chemical action. 2. Sarcastic or cutting; biting: "The caustic jokes ... deal with such diverse matters as political assassination, talk-show hosts, medical ethics" (Frank Rich). 3. Given to making caustic remarks: a caustic TV commentator. n. 1. A caustic material or substance. 2. A hydroxide of a light metal. 3. The enveloping surface formed by light rays reflecting or refracting from a curved surface, especially one with spherical aberration.
So many descriptions, I thought I'd single the one meaning out from the rest. I couldn't make up that description on my own.