v. in·vad·ed, in·vad·ing, in·vades
1. To enter by force in order to conquer or pillage: The Romans invaded Britain.
2. To enter as if by invading; overrun or crowd: Each weekend, skiers invade the mountain town.
3. To enter and proliferate in bodily tissue, as a pathogen: Bacteria have invaded the lungs.
4. To encroach or intrude on; violate: invade someone's privacy.
To make an invasion: The cancer had invaded deeply into his liver.
[Middle English, from Old French invader, from Latin invādere : in-, in; see IN-2 + vādere, to go.]
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.