Meaning

noun a serious (sometimes fatal) infection of rodents caused by Yersinia pestis and accidentally transmitted to humans by the bite of a flea that has bitten an infected animal

noun any epidemic disease with a high death rate

noun a pernicious and malign influence that is hard to get rid of

originFrom Middle English, from Old French, from Latin pestilentia (“plague”), from pestilens (“infected, unwholesome, noxious”); equivalent to pestilent + -ence.

Etymology from Wiktionary, CC BY-SA 3.0