a. An imaginary or legendary creature, such as a centaur or Harpy, that combines parts from various animal or human forms.
b. A creature having a strange or frightening appearance.
2. Archaic An organism that has structural defects or deformities.
3. Informal A very large animal, plant, or object.
4. One who inspires horror or disgust: a monster of selfishness.
Informal Extremely large; monstrous: a monster hit at the box office; ate a monster steak.
[Middle English monstre, from Old French, from Latin mōnstrum, portent, monster, from monēre, to warn; see men-1 in the Appendix of Indo-European roots.]
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.