Poisonous, a.
Having the qualities or effects of poison; venomous; baneful; corrupting; noxious. Shak. -- Poi"son*ous*ly, adv. -- Poi"son*ous*ness, n.
Shades of meaning
Fernald has no entry of its own for poisonous; he lists it under pernicious.
He lists it without comment; the entries above explain its neighbors.