The Collaborative International Dictionary of English v.0.48:

Deletery \Del"e*ter*y\, a. [LL. deleterius: cf. F.
   d['e]l['e]t[`e]re.]
   Destructive; poisonous. [Obs.] "Deletery medicines."
   --Hudibras.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Deletery \Del"e*ter*y\, n.
   That which destroys. [Obs.]
   [1913 Webster]

         They [the Scriptures] are the only deletery of
         heresies.                                --Jer. Taylor.
   [1913 Webster]