acid test

Noun

acid test (plural acid tests)

1. A test involving the reaction of an acid with another chemical.
2. (figuratively) A rigorous test or appraisal of the quality or worth of something.
   • [H]e reflected that few professional beauties could have stood, as this woman did, the acid test of that mercilessly brilliant morning.1912 October, Louis Joseph Vance, “The Spy”, in The Destroying Angel, New York, N.Y.: A[lbert] L[evi] Burt Company, →OCLC, page 152
   • "Eggs, Parker," said Freddie solemnly, "are the acid test!" / "Yes, sir?" / "If, on the morning after, you can tackle a poached egg, you are all right. If not not. And don't let anybody tell you otherwise."1920 April 10 – August 28, Pelham Grenville Wodehouse, chapter 1, in The Little Warrior [Jill the Reckless], New York, N.Y.: George H[enry] Doran Company, published 8 October 1920, →OCLC, section 1...
3. (broadly, historical) In the 1960s, a party based around the use and advocacy of the psychedelic drug LSD (known in slang as acid).
   • The Pranksters had just held an Acid Test at the Fillmore Auditorium, a big ballroom in the middle of one of San Francisco's big Negro slums, the Fillmore district. It was a wild night. Hundreds of heads and bohos from all over the Bay area turned out, zonked to the eyeballs.1968, Tom Wolfe, The Electric Kool-Aid Acid Test, New York, N.Y.: Farrar, Straus and Giroux, →OCLC, page 253