in·fil·trate (ĭn-fĭltrāt′, ĭnfĭl-)
v. in·fil·trat·ed, in·fil·trat·ing, in·fil·trates
a. To pass (troops, for example) surreptitiously into enemy-held territory.
b. To penetrate with hostile intent: infiltrate enemy lines; terrorists that had infiltrated the country.
2. To enter or take up positions in gradually or surreptitiously, as for purposes of espionage or takeover: infiltrated key government agencies with spies.
3. To cause (a liquid, for example) to permeate a substance by passing through its interstices or pores.
4. To permeate (a porous substance) with a liquid or gas.
To gain entrance gradually or surreptitiously.
One that infiltrates, especially an abnormal substance that accumulates gradually in cells or body tissues.
in·filtra·tive (-trə-tĭv) adj.
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.