Onagraceous \On`a*gra"ceous\, Onagrarieous \On`a*gra*ri"e*ous\, a. [From NL. Onagra an old scientific name of the evening primrose (Enothera), fr. Gr. ? a kind of plant; of uncertain origin.] (Bot.) Pertaining to, or resembling, a natural order of plants ({Onagrace[ae]} or {Onagrarie[ae]}), which includes the fuchsia, the willow-herb ({Epilobium}), and the evening primrose ({[OE]nothera}).