Emily Dickinson Lexicon

DEL-E-TE'RI-OUS, a. [L. deleterius, from deleo, to blot out or destroy; W. dilëaw, dilëu. Qu. Ir. dallaim, to blind.]

1. Having the quality of destroying, or extinguishing life; destructive; poisonous; as, a deleterious plant or quality.
2. Injurious; pernicious.