Definify.com

Webster 1913 Edition

Adj.

[Cf. F.

pestilentiel

Having the nature or qualities of a pestilence.

“Sends the pestilential vapors.”

Longfellow.

Hence: Mischievous; noxious; pernicious; morally destructive.

pestilential

, so infectious a thing is sin.

Jer. Taylor.

Adj.

Partaking of the nature of the plague or other infectious disease; as a pestilential fever.

Producing or tending to produce infectious disease; as pestilential vapors.

Mischievous; destructive; pernicious.

pestilential ‎(comparative more pestilential, superlative most pestilential)

Producing pestilence or plague; pestilent.
- 1941, Chapman Miske, The Thing in the Moonlight:
  Casting my eyes about, I beheld no living object; but was sensible of a very peculiar stirring far below me, amongst the whispering rushes of the pestilential swamp I had lately quitted.

pestilential m ‎(oblique and nominative feminine singular pestilentiale)