Definition of phenolphthalin in US English:

phenolphthalin

noun

Chemistry
  • A crystalline solid, (C₆H₄OH)₂CHC₆H₅COOH, which gives phenolphthalein when oxidized, and is used as an indicator.

Origin

Late 19th century; earliest use found in Journal of the Chemical Society. From phenol + phthalin.