caus·tic / ˈkôstik/ • adj. 1. able to burn or corrode organic tissue by chemical action: a caustic cleaner. ∎ fig. sarcastic in a scathing and bitter way. ∎ fig. (of an expression or sound) expressive of such sarcasm: a caustic smile. 2. 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. DERIVATIVES: caus·ti·cal·ly / -ik(ə)lē/ adv. caus·tic·i·ty / kôˈstisətē/ n.

caustic In optics, light focused by reflection from or refraction through a curved object. For example, when a magnifying glass is used to burn a piece of paper, the intense point of focused light at the paper's surface forms a caustic. Ray-tracing algorithms in computer graphics typically have difficulty correctly detecting and handling this phenomenon. An example might be the form of the sunlight on the bottom of a swimming pool when there are ripples on the surface of the water that focus the light into caustics.

caustic, any strongly corrosive chemical substance, especially one that attacks organic matter. A caustic alkali is a metal hydroxide, especially that of an alkali metal; caustic soda is sodium hydroxide, and caustic potash is potassium hydroxide. Silver nitrate is another caustic substance; it is sometimes called lunar caustic. Most inorganic acids, e.g., sulfuric acid, are caustic, especially when concentrated.

caustic corrosive XIV; fig. bitter XVIII. — F. caustique or L. causticus — Gr. kaustikós capable of burning, f. kaustós combustible, f. *kaf, base of kaíein burn; see -IC.

caustic (kaw-stik) n. an agent, such as silver nitrate, that destroys tissue. Caustic agents may be used to remove dead skin, warts, etc.

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