Source : Webster's Revised Unabridged Dictionary (1913)

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.

Source : WordNet®

deleterious
     adj : harmful to living things; "deleterious chemical additives"
           [syn: {hurtful}, {injurious}]