pestilentious
/ˌpɛstɪˈlɛnʃəs/adjective
Carrying, producing, or tending to produce pestilence; of the nature of or relating to pestilence; destructive to life or health; deadly. Now rare.
Origin
Late Middle English; earliest use found in Prose Life Alexander. From Middle French pestilencieux, pestillencieux, pestilentieux (French pestilentieux) corrupting, pernicious, contagious, of or relating to pestilence, catastrophic and its etymon post-classical Latin pestilentiosus destructive to life or health (3rd cent.), pernicious, evil (Vetus Latina) from classical Latin pestilentia + -ōsus. Compare Spanish pestilencioso, Italian pestilenzioso.