lysergic acid

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A crystalline alkaloid, C₁₆H₁₆N₂O₂, derived from ergot and used in medical research as a psychotomimetic agent.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun organic chemistry An organic compound, 6-methyl-9,10-didehydro-ergoline-8-carboxylic acid, derived from an alkaloid found in ergot; its amide derivatives are widely used as pharmaceuticals and as hallucinogenic drugs (LSD).

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a crystalline acid often used in medical research; obtained from ergotic alkaloids