acid

A conclusive test. The phrase comes from the 19th-century practice of testing metals in nitric acid to determine if they contained gold. Restructuring the organization will be the acid test that determines whether or not it can survive the sudden downturn in the economy.

To be under the influence of lysergic acid diethylamide (LSD), a powerful psychedelic drug commonly known as "acid." A lot of my friends like being on acid, but it just makes me feel really tense and paranoid.

To be unpleasant or offensive, usually due to speaking in a caustic or sarcastic manner. Often followed by "with (someone)." Don't come the acid with me, son, or I'll knock you upside the head. I try to avoid her whenever I can, for she's far too quick to come the acid.

slang To ingest the psychedelic drug lysergic acid diethylamide (LSD, or "acid"). I had a real bad trip last night. I'll never drop acid again. A lot of my friends like dropping acid, but it just makes me feel really tense and paranoid.

Under the influence of lysergic acid diethylamide (LSD), a powerful psychedelic drug commonly known as "acid." The man was reportedly on acid when claimed he could fly and tried to jump off the building.

To beg, importune, or proposition (someone) for something, such as a money loan, a favor (sexual or otherwise), or information. Primarily heard in Australia, New Zealand. My no-account brother-in-law is always putting the acid on for a money loan—which, I'll add, he has never once paid back. It's like he's surprised when women in a random bar don't all come up putting the acid on him.

Fig. a test whose findings are beyond doubt or dispute. The senator doesn't look too popular just now, but the acid test will be if he gets reelected.

A decisive trial to determine worth or quality, as in Exposure to brilliant sunlight is the acid test for showing this fabric won't fade. Alluding to a 19th-century chemical test for distinguishing gold from other metals, this term was used figuratively by the early 1900s.

COMMON If you call something the acid test, it will prove how effective or useful something is. The acid test for the vaccine will be its performance in the south where the disease is more widespread. So far, I don't feel too bad but I'm waiting for my first really stressful day when things go wrong. That will be the real acid test. Note: Nitric acid can be used to test whether a metal is pure gold because it damages most metals but does not affect gold.

A conclusive trial to establish the truth or worth of something or someone. The term comes from a test long used to distinguish gold from copper or some other metal. Most corrosive acids do not affect gold, but a solution of nitric acid and hydrochloric acid dissolves the metal. Used literally by jewelers in the late nineteenth century, the term soon was employed figuratively, by U.S. president Woodrow Wilson among others.