The Collaborative International Dictionary
lunar caustic
Nitrate \Ni"trate\, n. [Cf. F. nitrate.] (Chem.) A salt of nitric acid.
Nitrate of silver, a white crystalline salt ( AgNO3), used in photography and as a cauterizing agent; -- called also lunar caustic, and more commonly called silver nitrate.
Wiktionary
lunar caustic
n. (context chemistry obsolete English) silver nitrate prepared for use as a cautery
WordNet
lunar caustic
n. silver nitrate fused into sticks and formerly used as a caustic
Usage examples of "lunar caustic".
I took a piece of lunar caustic, which I wetted, and drew stripes and figures all over his weather-beaten face, increasing his natural ugliness to a frightful degree, and made him look very like a New Zealand warrior.