1 unpleasing or repulsive to see or hear (an ugly scar; spoke with an ugly snarl).
2 unpleasantly suggestive; discreditable (ugly rumours are about).
3 threatening, dangerous (the sky has an ugly look).
4 morally repulsive; vile (ugly vices).
Phrases and idioms:
ugly customer an unpleasantly formidable person. ugly duckling a person who turns out to be beautiful or talented etc. against all expectations (with ref. to a cygnet in a brood of ducks in a tale by Andersen).
Derivatives:
uglily adv. ugliness n.
Etymology: ME f. ON uggligr to be dreaded f. ugga to dread
Useful english dictionary. 2012.