caustic (KAW-stik) adjective
1. Capable of burning or corroding.
2. Highly critical; sarcastic.
[From Latin causticus, from Greek kaustikos, from kaustos (combustible), from kaiein, (to burn).] Caustic soda (Sodium hydroxide) is a highly corrosive substance used in the manufacture of soap, paper, and textiles.
"Some were outright sarcastic, others clearly caustic."
-- Vijay Mruthyunjaya; ICC's Hairobics Baffle; Gulf Daily News (Bahrain); Aug 28, 2006.
An example of caustic wit:
"She runs the gamut of emotions from A to B."
-- Dorothy Parker, speaking of Katharine Hepburn