\Pes`ti*len"tial\, a. [Cf. F. pestilentiel.]
1. Having the nature or qualities of a pestilence. ``Sends
   the pestilential vapors.'' --Longfellow.
2. Hence: Mischievous; noxious; pernicious; morally
   destructive.
         So pestilential, so infectious a thing is sin.
                                               --Jer. Taylor.