1. A subversive group or device placed within enemy ranks.
2. The hollow wooden horse in which, according to legend, Greeks hid and gained entrance to Troy, later opening the gates to their army.
3. Computers A program that appears to be legitimate but is designed to have destructive effects, as to data residing in the computer onto which the program was loaded.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2019 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.