Pestilential means carrying disease, or extremely annoying. A pestilential swamp, pestilential flies, that pestilential noise.
The literal sense is nearly gone and the exasperated one has taken over, which is a common fate for words about plague. It is now mostly comic. Note pestilence, and pest, which is the same root worn down to something much smaller.
1adjectivepestilentialCarrying disease, or extremely annoying.
“The early settlers died in their hundreds in the pestilential swamps along the coast.”
pestilential is a quality of nuisance.
Latin pestilentialis comes from pestilentia, plague, from pestis, a plague. Pest is the same root.
Latin
pestilentialis
English, today
pestilential
From Latin pestilentialis, from pestilentia.
Etymology from Wiktionary, CC BY-SA