1. Repulsive, especially to the sight; revolting. See Synonyms at ugly.
2. Morally offensive; detestable: hideous acts of torture.
3. Causing great harm or fear; terrible: a hideous disease.
[Middle English, variant of hidous, from Anglo-Norman and Old French hideus, hisdeus, probably from Old French hisde, hide, horror, fright (probably from alteration, with expressive initial h, of Frankish *egisida, fright, from Germanic *agisōn, from *agiz, fear), or perhaps from Vulgar Latin *hispidōsus, horripilating (from Latin hispidus, rough, shaggy, bristly; probably akin to hirsūtus, hairy, hirsute).]
hid′e·osi·ty (-ŏsĭ-tē) n.
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.