pestilential
pes.ti.len.tial \.pes-t*-'len-ch*l\ \-ch*-le-\ aj 1a: causing or tending to cause pestilence : DEADLY 1b: of or relating to pestilence 2: morally harmful : PERNICIOUS 3: IRRITATING, ANNOYING - pes.ti.len.tial.ly av
Webster's English Dictionarypes.ti.len.tial \.pes-t*-'len-ch*l\ \-ch*-le-\ aj 1a: causing or tending to cause pestilence : DEADLY 1b: of or relating to pestilence 2: morally harmful : PERNICIOUS 3: IRRITATING, ANNOYING - pes.ti.len.tial.ly av