adj. & n.
adj. 1 that burns or corrodes organic tissue. 2 sarcastic, biting. 3 Chem. strongly alkaline. 4 Physics formed by the intersection of reflected or refracted parallel rays from a curved surface.
n. 1 a caustic substance. 2 Physics a caustic surface or curve. caustic potash potassium hydroxide. caustic soda sodium hydroxide. caustically adv. causticity n.
[ L causticus f. Gk kaustikos f. kaustos burnt f. kaio burn ]