phenolphthalein
noun
phe·nol·phtha·lein ˌfē-nᵊl-ˈtha-lē-ən 
-ˈtha-ˌlēn,
-ˈthā- : a white or yellowish-white crystalline compound C20H14O4 used in analysis as an indicator because its solution is brilliant red in alkalies and is decolorized by acids and in medicine as a laxative
Example Sentences
Recent Examples on the Web Those ingredients included things like sibutramine, an appetite suppressant that was taken off the market due to the risk for strokes, as well as the laxative phenolphthalein. 
Sarah Jacoby, SELF, 17 Dec. 2020
Sarah Jacoby, SELF, 17 Dec. 2020 Word History
Etymology
International Scientific Vocabulary phenol + phthalein any of various xanthene dyes, from phthalic acid
First Known Use
1875, in the meaning defined above
Medical Definition
phenolphthalein
noun
phe·nol·phtha·lein ˌfēn-ᵊl-ˈthal-ē-ən -ˈthal-ˌēn
-ˈthal-ˌēn -ˈthāl-
: a white or yellowish white crystalline compound C20H14O4 that is used in analysis as an indicator because its solution is brilliant red in alkalies and is decolorized by acids and that is used in medicine as a laxative