Wiktionary
propiolic acid
n. (context organic compound English) An unsaturated organic acid, C3H2O2.
Wikipedia
Propiolic acid
Propiolic acid is an unsaturated carboxylic acid. It is a colourless liquid that crystallises to give silky crystals. Near its boiling point, it decomposes. It is soluble in water and possesses an odor like that of acetic acid.