Definition of ass's parsley in English:

ass's parsley

noun

  • (Also asses' parsley) any of several common umbelliferous plants resembling parsley or chervil but unpalatable or poisonous, including cow parsley (Anthriscus sylvestris), rough chervil (Chaerophyllum temulum), and especially fool's parsley (Aethusa cynapium).

Origin

Late 19th century; earliest use found in Richard Prior (1809–1902).