(optics) A curve to which the ray of light, reflected or refracted by another curve, are tangents, the reflecting or refracting curve and the luminous point being in one plane.

sodium hydroxide (NaOH), a strong alkaline substance used in the manufacture of paint, soap and detergents, or as a drain cleaner.

plural of caustic soda

quicklime

potash

(chemistry, obsolete) Silver nitrate fused into a stick and used for cauterizing.

Ammonia as a gas, or in solution.

plural of caustic alkali

(chemistry, dated) The hydrate of potassium (called caustic potash) or sodium (caustic soda).

plural of caustic surface