a. [ Cf. F. pestilentiel. ] 1. Having the nature or qualities of a pestilence. “Sends the pestilential vapors.” Longfellow. [ 1913 Webster ]
2. Hence: Mischievous; noxious; pernicious; morally destructive. [ 1913 Webster ]
So pestilential, so infectious a thing is sin. Jer. Taylor. [ 1913 Webster ]
adv. Pestilently. [ 1913 Webster ]