pestilential

1. (figurative) Having a harmful moral effect (especially one that is believed to spread in the manner of pestilence).Examples: "But as the Poisons of the deadliest kind Are to their own unhappy Coasts confin’d, […] So Presby’try and Pestilential Zeal Can only flourish in a Common-weal."; "By proclaiming individuals or entire societies to be damned, by treating their convictions as pestilential heresies, church and state had deliberately loosed fanaticism and savagery on often helpless men."Synonyms: perniciousfiguratively

2. (figurative) Causing irritation or annoyance.Examples: "There’s the pestilential nuisances who write for autographs […] They’d none of ’em be missed!"; "1899, Joseph Conrad, Heart of Darkness in Blackwood’s Edinburgh Magazine, Volume 165, March 1899, Chapter 2, p. 480, […] a species of wandering trader—a pestilential fellow, snapping ivory from the natives."; "“You are right that Authority must go. It is ridiculous—pestilential, not to be borne—that we should be ruled by an irresponsible dictator in all our essential economy!”"Synonyms: annoying, irritating, pestiferous, pestilent, troublesome, vexatiousfiguratively