Deleterious \Del`e*te"ri*ous\, a. [LL. deleterius noxious, Gr. dhlhth`rios, fr. dhlei^sqai to hurt, damage; prob. akin to L. delere to destroy.] Hurtful; noxious; destructive; pernicious; as, a deleterious plant or quality; a deleterious example. -- {Del`e*te"ri*ous*ly}, adv. -- {Del`e*te"ri*ous*ness}, n. [1913 Webster]