a. Shockingly hideous or frightful in appearance.
b. Of or resembling a fabulous monster.
2. Exceptionally large; enormous: a monstrous tidal wave.
3. Extremely immoral or cruel: a monstrous dictator; monstrous behavior.
4. Archaic Deviating greatly from the norm in appearance or structure; abnormal.
[Middle English, from Old French monstruos, from Latin mōnstruōsus, from mōnstrum, portent, monster; see MONSTER.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. 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.