CAUSTIC

I. adjective Etymology: Latin ~us, from Greek kaustikos, from kaiein to burn Date: 14th century capable of destroying or eating away by chemical action ; corrosive , marked by incisive sarcasm, relating to or being the surface or curve of a ~, ~ally adverb ~ity noun Synonyms: see: ~ II. noun Date: 15th century a ~ agent: as, a substance that burns or destroys organic tissue by chemical action, sodium hydroxide , the envelope of rays emanating from a point and reflected or refracted by a curved surface