Definition of onagraceous in US English:

onagraceous

adjective

Botany
  • Of or relating to the family Onagraceae, of which Onagra (now Oenothera) was the type genus, and which includes plants such as the evening primroses, willowherbs, and fuchsias.

Origin

Mid 19th century; earliest use found in William T. Brande (1788–1866), chemist. From scientific Latin Onagraceae, family name + -ous.

Pronunciation

onagraceous

/ɒnəˈɡreɪʃəs/