ružno

1. in an ugly way; unattractively
   Ova jakna ti baš ružno stoji. — That jacket really doesn't look good on you.
   Piše tako ružno da ništa ne mogu da pročitam. — His handwriting is so ugly I can't read a thing.
2. (of behaviour, speech) badly; meanly; rudely
   Ružno se ponašao prema svojoj majci. — He treated his mother badly.
   Nemoj ružno da pričaš o ljudima. — Don't speak badly of people.
3. (ružno je + inf.) it's not nice; it's wrong
   Ružno je lagati prijatelje. — It's not nice to lie to your friends.

For feeling unwell Serbians usually say loše, not ružno.