(Originally) the water dropwort Oenanthe pimpinelloides (obsolete); (now) the closely related plant O. lachenalii (which was formerly included in the species O. pimpinelloides).
Origin
Mid 19th century.
Definition of parsley water dropwort in US English:
parsley water dropwort
noun
(Originally) the water dropwort Oenanthe pimpinelloides (obsolete); (now) the closely related plant O. lachenalii (which was formerly included in the species O. pimpinelloides).