a. Causing or likely to cause epidemic disease: a pestilent swamp.
b. Infectious or epidemic: a pestilent disease.
c. Archaic Tending to cause death; deadly.
2. Morally or socially harmful; pernicious: pestilent writings.
3. Causing annoyance or disapproval: a pestilent fool.
[Middle English, from Old French, from Latin pestilēns, pestilent-, from pestis, pestilence; see PEST.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.